It’s a crucial day for Democrats trying to maintain control of Congress. The loss of either chamber could be disastrous for Biden.

The most important thing to remember for Nov. 9, the day after Election Day, is to be ready for the likelihood that the broad outcome – which party will control the House and Senate – may not be known for days or weeks.

CNN did not project that Joe Biden would win the 2020 presidential election until four days after Election Day.

It was not clear Democrats would control the Senate until two months later, on Jan. 6, 2021, when Jon Ossoff was projected to win the second of two runoff elections in Georgia.

There could be another “red mirage”: Projecting results can take time, and not because of any widespread fraud or conspiracy. Rather, it’s partially because a large portion of US voters are again casting their votes early and by mail.

While that’s far fewer pre-election votes than two years ago and the counting of these votes should go quicker in most states than it did in 2020, that doesn’t mean it will be instantaneous.

Back in 2020, multiple states had large portions of the vote uncounted as of noon the day after Election Day. That delay in 2020 was partially due to the Covid-19 pandemic, but it’s also because some states just take longer. California conducts elections mostly by mail and routinely has more than 30% of its vote uncounted by the next day.

If the race to control the House is close and certain California races are close, it’s entirely possible those races will need to play out to determine control.

Read more about what happens after Election Day here.

Overall, there are 309 women running for House, Senate or governor on midterm ballots across the country this year. Here’s how it breaks down: 

Political parties have more power when they control the House or Senate by winning a majority of the seats in that chamber. The party in power controls committees that write legislation and decides which measures will get a vote on the floor.

In the House, the party with at least 218 seats has the majority and, assuming it can unite behind one candidate, selects the Speaker of the House. In the Senate, the party with 51 votes has the majority.

The Democrats’ majority in Congress is currently razor-thin: The Senate is a 50-50 split (with Vice President Kamala Harris’ tie-breaking vote giving them the advantage) and Speaker Nancy Pelosi’s control of the House rests on a slim margin. In 2022, all 435 House seats and 35 of the 100 Senate seats are on the ballot.

Why are only a third of senators up for election? Senators serve six-year terms, and there are federal elections every two years. The seats are broken up into three classes, and about a third of the Senate is on the ballot every two years. The 2022 election features Class III senators. See the race ratings by Inside Elections.

Why are all 435 House members up for election every two years? The House of Representatives is the piece of the federal government that is closest to the people. Putting House members up for election every two years allows voters more direct and immediate control of the direction of their government.

Read up on other key terms to know for election night here.

Pennsylvania Democratic Senate nominee John Fetterman’s campaign has gone to a federal court to try to have Pennsylvania voters’ mail-in ballots counted if they weren’t signed with a valid date. A divided Pennsylvania Supreme Court recently ordered counties to refrain from counting mailed ballots with missing or invalid dates on their outer envelopes. But Fetterman is hoping the federal court will supersede the state court’s decision.

The question of whether mailed ballots with incorrect or missing dates can be counted is one of the hottest voting disputes in the pivotal state leading up to Election Day.

“The date on a mail ballot envelope thus has no bearing on a voter’s qualifications and serves no purpose other than to erect barriers to qualified voters exercising their fundamental constitutional right to vote. This unnecessary impediment violates the Civil Rights Act and the First and Fourteenth Amendments to the U.S. Constitution,” attorneys for Fetterman and the Democrats wrote in their new lawsuit filed Monday in the US District Court for the Western District of Pennsylvania.

Republicans have advocated for strict rules around mailed-in voting that would force ballots with missing information to be rejected.

Remember: Fetterman’s race against Republican nominee Mehmet Oz is one of the year’s marquee Senate races. Republicans view holding on to the seat of retiring GOP Sen. Pat Toomey as key to their hopes of capturing the Senate majority, while Democrats see flipping seats in Pennsylvania and Wisconsin, both states carried by now-President Joe Biden in 2020, as the best way to gird against losses elsewhere.

CNN’s Jessica Dean contributed to this report.

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President Joe Biden offered a bluntly dire assessment during a fundraiser last Friday in Chicago. “If we lose the House and Senate, it’s going to be a horrible two years.”

Biden himself has been projecting optimism in the final days of the campaign, but reality is setting in for Democrats: their majority rule in Congress could soon end, and Biden’s ability to get his top priorities passed could go with it.

Here are four areas that are at stake this Tuesday for Biden and his administration:

GOP investigations: Republicans on Capitol Hill have made abundantly clear that if they take control of Congress, Biden should brace for investigations targeting him, the White House and even members of the his family.

GOP lawmakers including Reps. James Comer and Jim Jordan, who are likely to chair the House Oversight and Judiciary committees respectively, are getting ready to probe a range of issues, from the business dealings of Biden’s son, Hunter; to what Republicans allege is political interference by the FBI and Justice Department; to the origins of the Covid-19 pandemic.

Agenda: If Republicans gain control of one or both chambers, the era of big, progressive bills will likely end. Instead, Biden will be on the defense as Republicans work to undo much of what he accomplished in the first two years of his term. The GOP has already vowed to roll back elements of Biden’s signature legislation, the Inflation Reduction Act, including its new, higher taxes on corporations. And they could work to roll back or challenge some of the president’s climate initiatives that are included in the package.

Biden’s 2024 decision: As soon as the 2022 midterm election results are in, national attention will immediately turn to 2024 – including on the question of whether Biden will seek a second term. For weeks, the president and his advisers have maintained that his intention, for now, is to run again. They’ve also said that no decision is final until the president has had ample opportunity to discuss his political future with his family. But Biden’s 2024 decision won’t just be a family affair – there will also be strong political dynamics at play.

Staffing changes: Biden has seen remarkably little turnover in the first two years of his tenure among his Cabinet and senior team. His inner circle remains mostly intact. That includes chief of staff Ron Klain, senior advisers Mike Donilon and Steve Ricchetti, deputy chiefs of staff Bruce Reed and Jen O’Malley Dillon, communications director Kate Bedingfield and top communications adviser Anita Dunn. Officials have said changes are possible both to the president’s Cabinet and his senior White House staff later this year, though no moves are guaranteed. Should Biden announce his decision to run in 2024, several of the members of his core team are considered likely to shift over to the political operation.

The 2022 midterms have arrived and here are seven things to watch in Tuesday’s midterm elections:

Who will control the House: Of all the major storylines on Tuesday evening, this is one that few Democrats dispute: It is unlikely the party will control the legislative chamber come January. Given Republicans only need a net gain of five seats to take the majority, the odds of the GOP taking back the House are high. The party is on offense in House race across the country, but most notably in districts Biden won handily just two years ago, including once seemingly solid blue districts in Rhode Island, New York and Oregon.

Who will control the Senate: If control of the House feels like more of an unavoidable loss for Democrats, control of the currently evenly divided Senate offers a surprising bright spot for the party — aided by voters harboring unfavorable feelings about Republican candidates while also disapproving of Biden’s job performance. The most vulnerable Democratic incumbents are on the ballot are in Nevada, New Hampshire, Arizona and Georgia, where polls show each of those races are tight. The party is on offense in Pennsylvania and Wisconsin, two states Biden won just two years ago.

Election deniers in key swing states: Republicans who have parroted former President Donald Trump’s lies about widespread voter fraud are seeking to take charge of some swing states’ election machinery. The outcomes in those states could have dramatic consequences in 2024, with Trump on the verge of another presidential bid and candidates in crucial swing states seeking positions that they could attempt to use to undercut voters’ will.

Will Latino voters continue rightward shift: Republicans will watch whether they built on the gains that Trump made among Latino voters two years ago. Three House races in the heavily Hispanic Rio Grande Valley in Texas will tell part of the story. Latino voters also make up crucial portions of the electorate in Arizona, Nevada and Miami-Dade County in Florida.

The impact of presidential politics: “If we lose the House and Senate, it’s going to be a horrible two years,” Biden said at a fundraiser on Friday. It’s an argument former President Barack Obama, who stumped for candidates in Georgia, Michigan, Wisconsin, Nevada, Arizona and Pennsylvania over the last few weeks, made explicitly during his final rally in Philadelphia on Saturday.

The wave-makers (or breakers): The shape of Congress over the next two years could become pretty apparent within the first few hours after the polls close on the East Coast — even if a handful of big races are too close to call. For Democrats, defeat in even two out of three of the contests would portend a very, very bad night. The party, both nationally and in certain states, has increasingly invested its electoral fate on the notoriously fickle suburbs. If a Republican wave is coming, the first sighting of high tides will be up and down the Atlantic seaboard.

The wait: As most Americans learned two years ago, Election Day can be a misnomer. Tuesday is when voting ends. But, in many states, it’s also when counting begins. That means a lot of hotly contested races could take into the wee hours or even later this week to be decided. That’s partially the nature of counting — and sometimes recounting — but it’s also due to state laws that instruct poll workers how to do their jobs and, in some states, make them hold off on doing them until later in the day.

In the contentious Georgia Senate race, Democratic Sen. Raphael Warnock, the first Black senator from Georgia who, along with Jon Ossoff, delivered control of the chamber for Democrats in a pair of January 2021 runoff elections, is once again on the ballot. Now, though, the pastor of Ebenezer Baptist Church is trying to win his first full term against Trump-backed football star Herschel Walker.  

Walker’s campaign has been dogged by scandals, including past allegations that he threatened women with violence, claims he has denied. The race was further rocked by a report in early October that Walker paid a woman to have an abortion in 2009. CNN hasn’t confirmed that allegation and Walker has also repeatedly denied it. Walker also has a made a series of verbal stumbles on the campaign trail, like when he criticized efforts to reduce air pollution by saying China’s “bad air” “moves over to our good air space.”  

Despite Walker’s struggles, Georgia only recently shifted towards Democrats, so the race is expected to be close. If no candidate wins a majority, the top two will compete in a Dec. 6 runoff. 

There are also key House races happening in the state:

Poll times: Polls close across the state at 7 p.m. ET. 

Political landscape: Atlanta and its inner suburbs are the most solidly Democratic regions of the state. The city’s outer suburbs have historically supported Republicans, but many of these affluent areas have moved towards Democrats in recent years.  

Americans head to the polls today for an election that has state and local officials across the country on edge as they brace for potential problems at the polls, contentious legal fights over ballots and fighting disinformation about the vote itself.

The hyper-polarized political climate has seen the vote itself come under a sustained barrage of attacks and disinformation for the better part of two years amid repeated false claims from former President Donald Trump that the 2020 election was stolen.

Early voting has provided a preview of the potential issues both big and small that could arise on Election Day, from armed ballot box watchers in Arizona accused of conspiring to intimidate voters to a legal fight over technical errors invalidating mail-in ballots in Pennsylvania.

Legal fights: In all, there have been about 120 legal cases surrounding voting filed as of November 3, compared to 68 before election day in 2020. More than half of the cases have sought to restrict access to the ballot, according to the Democracy Docket, a liberal-leaning voting rights and media platform that tracks election litigation.

In Pennsylvania, some counties are urging voters to correct absentee ballots with missing or improper dates that the state Supreme Court ordered to be set aside, while a federal legal challenge over is still looming. In Michigan, meanwhile, a judge rejected a lawsuit Monday from the GOP secretary of state candidate seeking to throw out absentee ballots in Democratic-heavy Detroit.

Georgia’s Cobb County on Monday extended the deadline for roughly 1,000 absentee ballots to be turned in until Nov. 14, after the ballots were not mailed out until just days before Election Day due to procedural errors in the election office.

Possible conflict with election deniers: In Arizona, the secretary of state’s office has sent 18 referrals to law enforcement related to drop-box intimidation, including a threatening message toward a government worker and several voters reporting being filmed at drop box locations in Maricopa County last week. A federal judge earlier this month imposed new restrictions against a right-wing group in the state following complaints about aggressive patrols of ballot boxes in the state, including blocking the members from openly carrying guns or wearing body armor.

CNN’s Jason Morris contributed to this report.