What happens if Donald Trump drops out of the presidential race before election day?

After leaked audio tape released Friday revealed Republican presidential nominee Donald Trump bragging about grabbing women without consent, and a tone-deaf apology, the distinct possibility that Trump may drop out of the race has bubbled up again. 

The prospect of dropping out, and the calls to do so, have plagued Trump for some time. In August, the Wall Street Journal and Last Week Tonight host John Oliver issued a passionate plea for Trump to pack up and leave. After the leak on Friday, Utah Gov. Jon Hunstman told the Salt Lake Tribune the "time has come for Governor Pence to lead the ticket." 

But what would happen if he did drop out? Is it legal? Is there precedent?

According to New York Magazine national affairs editor Gabriel Sherman's Twitter account, Alabama Senator Jeff Sessions is currently in a meeting with Trump urging him to drop out of the race. 

Last night during the post-leak fracas, NBC News director Chuck Todd tweeted that if the GOP didn't replace Trump by Sept. 1, they were stuck with him. 

It might be too late. 

The tweet tells the truth: Trump, and the Republican party, have very few options. Early voting has already begun in several states and Trump's name already appears in the Republican nominee's slot. 

Trump also can't hand the nomination to just anyone, even his running mate, Indiana governor and infamous homophobe Mike Pence. 

According to Ballotpedia, the GOP would have to replace Trump through a formal process: either reconvene all 2,472 delegates at another convention or let its 168-member body cast votes for a new nominee. In the second case, members are allowed to cast a number of votes that corresponds to how many delegates they had at the convention — more populous states get more votes.

It's never been done before. 

No presidential candidate has ever dropped out, though vice presidential candidate Thomas Eagleton resigned from being George McGovern's running mate after only 18 days. 

Eagleton wasn't well vetted and he had prior mental health issues that led to pressure to drop him from the ticket.  McGovern and his new running mate, Sargent Shriver, went on to suffer one of the worst presidential defeats ever. Opponents Richard Nixon and Spiro Agnew defeated McGovern and Shriver with the widest popular vote margin in history. 

Who would replace him? 

There's no telling who would be next in line. Pence did not originally seek the office during primary season, but according to a new Politico poll, he's the most popular choice for a run in 2020. 

Of respondents, 22% want Pence to run in 2020, while Trump and Paul Ryan each have 13% of the vote. Texas Sen. Ted Cruz has 12% of the vote, Florida Sen. Marco Rubio has 11% and Ohio Gov. John Kasich is at 7%. 

This may all be for nothing. On Saturday afternoon, Trump said he is not quitting, the Washington Post reported. 

Who knows if he's telling the truth. Trump has had a little trouble with the facts before. But, no matter what happens, it's gonna be messy.