Second, there’s the chance that the House of Representatives has to step in if no candidate clears the 270 electoral-vote threshold needed to win the presidency. While more clear-cut legally, this situation would still create a confusing moment in which each state delegation gets to cast just one vote for president. So even though Democrats control the House, they wouldn’t necessarily have the advantage, angering swaths of the country.

The possibilities are remote, but under a norm-busting administration, in a norm-busting year, with a hyperbolically divided public, the two parties are not taking any chances. Republicans and Democrats have already placed thousands of lawyers across the country to study the law in battleground states and prepare for these potential fights.

Democrats are worried Trump — who has already repeatedly refused to commit to conceding defeat — will cast suspicion on swing-state vote counts or even pressure state lawmakers to certify his desired results if there is a drawn-out counting process.

“We need to prepare for everything. Absolutely. We have invested too much time, money, energy,” said former Virginia Gov. Terry McAuliffe, who served as chairman of the Democratic National Committee. “Let me be clear. There is no low that Donald Trump will not go to, so we have to be prepared for that. … We don’t know what this guy is going to do.”

While the Republican National Committee said it is more focused on its $20 million effort to legally challenge pandemic-era voting rule changes, Trump’s team has discussed the possibilities that Congress might step in to determine the election, or that a state tries to certify two conflicting results, according to three people familiar with the conversations.

“Having been in a close election before, you have to have the lawyers lined up,” said Pat McCrory, the former Republican governor of North Carolina, who lost his 2016 reelection bid by 10,000 votes out of more than 4.6 million ballots cast. “Everybody should prepare for everything. They have no choice but to do that.”

Trump has predicted the Supreme Court could end up determining the winner and even publicly mused about a deadlocked Electoral College making its way to Congress. In turn, Speaker Nancy Pelosi has even asked Democrats to consider a possible House fight for the presidency as they determine where to spend election money.

While most polls show Trump lagging behind Biden in the swing states he needs to secure a second term in office, some key states, including Pennsylvania and North Carolina, remain extremely tight.

“In a close election, especially this close presidential election, whatever side is down is going to try everything they possibly can,” said Benjamin Ginsberg, a nationally recognized elections lawyer who represented four of the past six Republican presidential nominees and has blasted Trump’s rhetoric on voting.

While the country has become accustomed to declaring a winner on the evening of Election Day, close races can linger for days or even weeks as states finalize vote tallies — rounding up overseas ballots, for instance — or conduct recounts.

In 2020, the chances of a delayed result have gone up because of the pandemic. A record number of voters — more than half — are expected to cast their ballot by mail as Americans avoid the polls, possibly lengthening vote-counting time frames in battleground states where the margins are expected to be razor thin.

Michigan, Wisconsin and Pennsylvania — which Trump narrowly won in 2016 after years of Democratic presidential victories — could be the slowest to determine a winner because election officials are not allowed to start processing remote ballots days or weeks early like other states.

"We are well prepared for any scenario,” said Biden spokesman Michael Gwin.

Republicans argue it’s Biden’s team that will never concede. “Here’s a possible outcome we should be concerned about: Joe Biden doesn’t accept the results when President Trump wins reelection, following Hillary Clinton’s call for Biden not to concede ‘under any circumstances,” said Trump campaign spokesperson Thea McDonald.

But some worry that Republicans haven’t prepared enough. Tom Fitton, president of Judicial Watch, a conservative group that has filed lawsuits over the accuracy of voting rolls in some states, said he’s frustrated the Republicans haven’t taken the possibility of a House fight seriously enough.

“Nothing is off the table,” he said.

Election observers worry the mutual suspicion could quickly turn ugly in the election’s aftermath if there is any question about the results. In June, the Transition Integrity Project, a bipartisan group of 100 experts, including former federal employees, pollsters and strategists, simulated what could happen the day after Election Day if Trump contested the results. They took into consideration the potential lawsuits and recounts that would result, according to a person familiar with the exercise.

“Virtually all ended with street-level violence and a constitutional crisis,” the person said.

All states are under a set timeframe to sort through all the anticipated 2020 mail-in ballots.

By Dec. 8, each state must certify its results to Congress, giving each only five weeks to navigate any disputes and recounts. In the contested 2000 election, Florida was still conducting a recount just days before that year’s Dec. 12 deadline when the Supreme Court stepped in to stop the process. And this past summer, it took longer than five weeks to count all ballots in a Democratic primary for a U.S. House seat in New York.

For the fall election, several states have extended deadlines to receive ballots due to fears the beleaguered U.S. Postal Service won’t be able to deliver millions of extra ballots on time. As a result, it could take longer than usual to tally some results. One candidate could declare victory in a state on election night, while another claims victory after more mail-in ballots have been counted.

Concerned about these possible delays, Sen. Marco Rubio (R-Fla.), proposed a bill that would move the Dec. 8 deadline back to Jan. 1. It has not gone anywhere.

Traditionally, each state’s electoral votes go to whoever wins the popular vote in that state, but the process to get there is not always simple. Once the popular vote winner is determined in a state, the state appoints electors from the prevailing party to the Electoral College.

But if a state reaches the deadline without a winner, it becomes unclear which electors should be appointed. And it’s possible that in such a scenario, a state’s legislature may appoint electors to certify the result they want. But that wouldn’t necessarily stop a governor or secretary of state from appointing a separate set of electors to certify a different result.

“This would be incredibly unlikely,” said RNC Chief Legal Counsel Justin Riemer. “We believe a recount or election contest would dispose of those issues.”

Yet in 2000, just days before the Supreme Court essentially ended the race between George W. Bush and Al Gore, the Florida legislature was poised to send Republican electors to certify the election, regardless of the result of an ongoing recount. Part of their reasoning? The looming deadline to give results to Congress.

“The legislatures’ efforts to intervene in this rather radical way gets more and more plausible if the count is taking longer and longer and you’re edging up to the deadline,” said Paul M. Smith, vice president for litigation and strategy of the Campaign Legal Center, which supports unrestricted access to voting, and a member of the National Task Force on Election Crises.

Four swing states have Republican legislatures and Democratic governors — North Carolina, Michigan, Wisconsin and Pennsylvania. One state — New Hampshire — has a Democratic legislature and Republican governor. Both setups could lead to a governor and state legislature disagreeing about who won the state, and trying to appoint competing sets of electors.

Pennsylvania is garnering the most attention, as it’s likely to be the tightest of these states.

“It would be negligent for the state’s legislature not to appoint delegates, especially when you consider the amount of resources that went into the race,” said Bryan Lanza, a 2016 Trump campaign official who is close to the 2020 team.

While the Constitution and federal law give legislatures the power to pick electors, each state has established its own process to follow, and many of them are vague.

It could get messy.

“If they aren’t confident that they believe the result, some legislatures will be tempted to take the authority and appoint electors directly,” said Barry Burden, founding director of the Elections Research Center at the University of Wisconsin, Madison.

If Congress is presented with two sets of elections, it would be forced to decide which to choose, with almost no playbook to follow. And if the two chambers of Congress are divided — likely because they are controlled by different parties, as they are now — it’s unclear what would happen, according to experts.

The scenario has played out just once before, in 1876, arguably the most contentious election in U.S. history. That year, three states — Florida, Louisiana and South Carolina — produced different sets of electors. Congress created a commission, which voted along party lines to select Republican Rutherford B. Hayes as president.

Just over a decade later, Congress passed a law that established a procedure for counting electoral votes, and the issue has never again been crucial to an election’s outcome. Hawaii did once submit two sets of electors in 1960.

Another crisis could come a few weeks later, when Congress meets to certify the presidential election on Jan. 6, 2021.

Normally, the process is a formality. But if the election is so close that neither Trump nor Biden has secured 270 electoral votes, the fate of the presidency ends up in the House of Representatives — a phenomenon that has only happened in 1800 and 1824, when no candidate won a majority of electors.

In this scenario, every state’s delegation gets a single vote based on an internal tally of each lawmaker in the delegation. It means the presidency may not be decided by the party that controls the House itself, but by the one that controls more state delegations in the chamber.

Currently, Democrats control the House, but Republicans control more state delegations. But since the final certification will occur after the newly elected Congress is sworn in, the 2020 House races could affect the delegation balance.

Because of this possibility, Pelosi has urged her Democratic colleagues to consider the House’s possible role in determining the 2020 election when choosing where to focus resources on winning seats in November. Flipping just a few seats in states like Montana and Alaska, for instance, could change the majority control of those state’s delegations.

Currently, Republicans control 26 delegations, Democrats have 22. Pennsylvania is tied and Democrats hold a 7-6 advantage in Michigan, with one seat held by independent Justin Amash.

“The idea that the United States of America — one of the oldest democracies and a long standing democracy — which has not had such a problem in years is now going to have a problem just because Donald Trump is inventing it is outrageous,” said David Lublin, an elections expert at the government department at American University.