From Hillary Clinton’s perspective, why wouldn’t she run for president a third time? From her perspective, voters who sat out 2016 or waffled and ultimately landed on Donald Trump have made known their regrets. U.S. intelligence has confirmed that Russia interfered ahead of the election to undercut her. And she won 2.9 million more votes than Trump, whose approval ratings are abysmal.

Despite all of that, the chance of Clinton actually running again seems remote. But CNN’s Jeff Zeleny said Sunday that people in her orbit indicate that she’s not willing to completely rule it out.

Perhaps she sees the rehabilitation of House Speaker Nancy Pelosi’s image — from divisive figure to democracy savior — as a window into what is possible. Or maybe it’s just really hard to let lifelong dreams die so close to being realized.

Of course, there’s a laundry list of reasons she shouldn’t run. The field is not cleared for her this time as it was in 2016. The competition would be fierce, including a number of female candidates. Trump would love nothing more than to re-litigate her emails or his (unfounded) conspiracy theories about the FBI’s support for her. And even among those Democrats who don’t blame her campaign’s miscalculations for Trump’s win, there is a still a widespread sense that it’s time to move on.

But there’s also the reality that if past is prologue, it would be unprecedented for a former nominee to come back and win the White House. It’s already quite rare for a party’s nominee to get a second crack at it. The last instance of a failed presidential nominee who ran for a second time and won was Richard Nixon in 1968.

Before that, the last party nominee to run again and win was William Henry Harrison, who lost to Martin Van Buren in 1836 but beat him four years later. (President Grover Cleveland lost his re-election in 1888 and, but won the office back in 1892.)

Others fared worse on the second go-round. Democrat Adlai Stevenson II lost twice to Republican Dwight D. Eisenhower. Thomas Dewey lost in 1944 to Franklin D. Roosevelt and four years later to Harry S. Truman.

There’s little indication that things would be any easier for Clinton in 2016. Unlike many politicians whose image improves once they’ve stopped seeking office, Clinton’s image has actually deteriorated since the 2016 election. Although 87 percent of Democrats had a favorable opinion of her the week of the election, that quickly dropped to 76 percent after she lost and remained around there as of September 2018, according to Gallup polling.

As about five months ago, the last time Gallup polled support for Clinton, her overall approval was at an all-time low of 36 percent — just as bad as Trump’s.

JM Rieger contributed to this report.