As questions swirl over whether Donald Trump will willingly bow out as the Republican nominee, or be forced out, pundits have labeled such an event as “unprecedented.” Yet there have been cases in American political history where a nominee has been forced to the sidelines, and a replacement has been named.

It’s pretty rare in American presidential history, but there have been cases of nominees that didn’t make the final contest. The most famous one occurred in the 1872, when Horace Greeley died after the election, but before the Electoral College met.

This Democratic Party nominee won only six of 37 states against President Ulysses S. Grant, so it was not really close. But when the Electoral College met, he only received three of the 66 votes he was supposed to get.

But there have been other cases, involving contests for governor, the U.S. Senate and the U.S. House of Representatives. And in each case, the party dealt with the issue differently. They major party could have backed a third party candidate, hoped for enough votes from the contest to appoint a replacement afterwards, but in most cases, the party chose to a name a replacement before the election, with varying degrees of success.

In 2006, Republicans had to deal with Florida Congressman Mark Foley, accused of inappropriate relationships with House of Representative pages. It was too late to change the ballot, but the GOP tried to have state legislator Joe Negron replace him. The slogan “Punch Mark For Joe” was funny, but ineffective, as Democrats took that longtime Florida district.

In 2002, U.S. Sen. Bob Torricelli (D-NJ) had won the nomination, but was forced to drop out after allegations about campaign gifts he accepted. Luckily, the Democrats had former U.S. Sen. Frank Lautenberg, who had retired two years earlier, but was willing to get back into politics.

Republicans cried foul, but Sen. Lautenberg beat Doug Forrester, a businessman. Similarly, in 1990, conservative GOP nominee Jon Grunseth stepped aside just days before the election after allegations of forcing teenage girls to skinny dip in a hot tub, and had extramarital affairs. His replacement, State Auditor Arne Carlson, pulled a huge upset over Minnesota Gov. Rudy Perpich, nicknamed “Governor Goofy.”

In some cases, the candidate dies just before the election. Missouri Gov. Mel Carnahan died in a plane crash, while state Sen. Tommy Burks was killed by his opponent, Byron “Low Tax” Looper. In both cases, wives were named to the ticket, after and before the election, with success for the Democrats.

The Republicans could stay with Trump, and hope he doesn’t drag down the party too badly. Of course, some in the GOP are more afraid that he’ll win than anything. And Trump doesn’t seem too concerned about the Republicans, as he said he wouldn’t mind if the party lost their majority in the U.S. Senate, as it would make him “a free agent.”

The Republicans also could name a replacement. But who would they pick among the fallen nominees. Former Florida Gov. Jeb Bush would be seen as “too establishment” for the anti-establishment Trump crowd.

Taking Pence makes it look like a GOP insider coup. There’s too much bad blood between Trump and Cruz supporters for the Texas Sen. to be the pick. Rand Paul and Marco Rubio is trying to save the GOP senate lead, while Scott Walker, Carly Fiorina, Rick Santorum, Rick Perry or Dr. Ben Carson just smack of desperation.

In the cases where a replacement worked, there was a good candidate, or spouse, ready to step in. And Melania Trump, after her RNC speech, inspires no confidence.

The best option for a toxic candidate may be to go with another political party nominee. And there is one. With two-term GOP Gov. Gary Johnson from New Mexico, and two-term GOP Massachusetts Gov. William Weld on the Libertarian Party ticket, the answer is obvious for Republicans. Such choices would fit with the smaller government, anti-establishment trend the party is looking for, with more experience than Trump ever had.