The modern US presidential concession call, in which the losing candidate reaches out to the winner to say “Hey, it’s yours, good luck,” started in 1896, when William Jennings Bryan sent William McKinley a well-wishing telegram. More recently, Hillary Clinton called Donald Trump on election night 2016 to congratulate him and offer her support. (“He was so shocked,” Clinton told Howard Stern in December. “He was more shocked than me I think.”)

Throughout the nail-biting vote count, Trump has made clear that he wouldn’t consider a victory for Joe Biden legitimate. In a rambling press conference this week, Trump made baseless claims of corruption and fraud. “If you count the legal votes, I easily win,” he said. “If you count the illegal votes, they can try to steal the election from us.” Whether Trump would ever give Biden a congratulatory or concessionary phone call is very much an open question.

So what happens if a president never concedes? Most immediately, not much. There’s no law requiring a written or verbal handover of the presidency between an incumbent and their successor. Trump refusing to make that call is sort of like an athlete refusing to shake hands at the end of a game: poor form, but otherwise inconsequential. (Similarly, it’s hard to imagine Trump seated behind Biden at an inauguration ceremony as the latter is sworn in.)

Still, there are plenty of ways beyond etiquette in which things could get complicated. In August, the Transition Integrity Project (TIP)—a bipartisan group of 100 current and former senior government officials and election experts—released a report outlining in great details how a contested election might play out (pdf). Here are a few possibilities:

1️⃣ Taking the vote counts to court

Trump has filed several lawsuits in swing states, in a strategy that hinges on a unique dynamic of this year’s vote. Because of the coronavirus, a record 65 million-plus ballots were cast by mail. Democrats were more likely to vote by mail this year, so these ballots have thus far disproportionately favored Biden. That means results coming in on election day tended to favor Trump but shifted as absentee ballots were counted—what’s called a “red mirage.” Trump has seized on this to falsely allege widespread fraud. So far, the courts have mostly not sided with him, but even one favorable ruling by a state supreme court could lead to a battle that makes its way to the US Supreme Court.

There is precedent here. In 1960, Richard Nixon conceded despite contested results in Illinois, and in 2000 Al Gore conceded after the Supreme Court’s 5-4 decision halting a Florida recount. To succeed in his legal challenges, Trump would need to provide evidence of fraudulent ballots in specific precincts.

2️⃣ Using the electoral college

States allow the popular vote to determine the appointment of electors, but Trump and his allies could use friendly state legislatures and governors to send alternate—or in the case of states with Republican legislatures and Democratic governors, additional—electors. When the electoral college convenes on Dec. 14, states with competing electors would cast double their allotted votes, forcing Senate president Mike Pence to figure out what to do with the doubled-up votes. If Pence threw out the extra votes and neither candidate hit 270, the decision goes to the House. There, each state delegation gets one vote; currently, in 27 states, a majority of delegates are Republican.

(For a trip down memory lane: Back in 2000, Florida’s Republican legislature was on the cusp of appointing new electors to vote for Bush as the court-ordered recount dragged on. The SCOTUS decision rendered that preparation moot. Also, in 1876, states sent competing electoral college delegations and after Congress failed for months to agree on which was valid, a last-minute deal was struck that made Rutherford B. Hayes president as long as he agreed to end Reconstruction.)

2️⃣ (b) Pelosi goes nuclear

Theoretically, according to the Atlantic, House speaker Nancy Pelosi could prevent members of the House from entering the chamber to witness Pence’s vote count, which must happen “in the presence of” the governing body. If she announces plans to stall indefinitely, like through Inauguration Day, she could then claim her own right to the presidency through the line of succession.

3️⃣ All of the above

Those first few prospects aren’t mutually exclusive. Biden could win, Pence could use conflicting electoral votes to assert a Trump victory, and Pelosi could stall her way into a technical win unless Pence accepts Biden’s victory. All three claims to the presidency would be supportable.

In all of these scenarios, a good deal depends on how GOP officials contend with Trump’s strategy. Some of the more alarming scenarios mapped out by TIP—including a Trump attempt to federalize and deploy the National Guard—may lack for Republican support. Already, members of the party are distancing themselves from Trump’s denigrations of the election process.

Of course, there’s also the possibility that Biden wins, the courts confirm it, and Trump simply refuses to leave the White House come January. The Constitution doesn’t leave much wiggle room on this front: The 20th amendment says that “The terms of the president and vice president shall end at noon on the 20th day of January, and the terms of their successors should then begin.”

“I think we would have that Nixonian moment where a leadership team would travel to the White House to declare, ‘Mr. President, it is over,’ ” Michael Steele, a former Republican National Committee chairman who participated in TIP exercises, told the Boston Globe. And of course, the Secret Service or the US Marshals could at that point boot private citizen Trump as a trespasser.

“If you’ve got a president who’s chained himself to the Resolute Desk,” Steele said, “the new president would say, ‘Would you go inside and get him out please?’ ”

With contributions from Annabelle Timsit.

Read more of Quartz’s election coverage

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