In 2016, there were 17 prominent Republican candidates for president — an enormous total that seemed unlikely to ever be matched again. Ah, those were simpler times. It’s not even 2020 yet, but there are already 16 major candidates in the Democratic race for president. And the glut of candidates has some observers asking whether the incentives to run are not what they should be. That is, running for president raises a candidate’s profile and might give them the opportunity to fail up to a Cabinet post or a cushy cable-news gig after the election. As my colleague Galen Druke recently asked on Twitter, “Are there any reasons not to run for president even if you think you can’t win?”

As I see it, there’s one big reason not to run: if you stand to lose a prestigious job. Indeed, most of the people currently in the Democratic presidential race do not have to sacrifice their current jobs to run; the same is true of several prospective candidates. This fact could explain why so many lower-tier contenders are dipping their toes in the water despite having low odds of winning the nomination. Here’s a look at which candidates (and potential candidates) are risking their careers by running and which ones can fall back on their current jobs should they lose.

First, six of the Democratic candidates in the 2020 race are U.S. senators, and maybe that’s no surprise: Two-thirds of the Senate can effectively take a free shot at the presidency in 2020 because they aren’t up for re-election. Some of the race’s biggest names are drawn from this pool, including Kamala Harris, who does not face re-election in California until 2022, as well as Kirsten Gillibrand of New York, Amy Klobuchar of Minnesota, Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts, who aren’t up until 2024. Colorado Sen. Michael Bennet, who is considering a run, is also not up for re-election until 2022. This means that each of these candidates can lose the presidential primary and still keep their seats in the Senate.

A couple of mayors and a governor also don’t have to worry about leaving their current jobs behind by running for president. Rumored hopefuls Montana Gov. Steve Bullock and New York City Mayor Bill de Blasio can’t seek re-election to their current positions anyway, because of term limits. And Miramar, Florida, Mayor Wayne Messam (who is an active presidential candidate but not yet a major one by our standards) was re-elected this year, so he has nothing to lose by running.

And then there are several candidates who don’t currently hold political office in the first place. Beto O’Rourke ran (unsuccessfully) for Senate in Texas last year rather than seek re-election to his U.S. House seat, so he’s been out of Congress since January. Julian Castro’s last political job was secretary of housing and urban development in the Obama administration, and that ended when President Trump’s tenure began. Term limits prevented John Hickenlooper from running for re-election as the governor of Colorado in 2018. And businessman Andrew Yang has never held political office (same with not-yet-major-candidate Marianne Williamson). Also in this category are some politicians who have yet to jump into the race, including former Georgia state House Minority Leader Stacey Abrams, former Vice President Joe Biden and former Virginia Gov. Terry McAuliffe.

That leaves only a few presidential candidates who hold elected offices that are up for re-election this cycle. However, that’s not an automatic reason to rule out a presidential bid. Luckily for these hopefuls, a handful of states allow candidates to run for multiple offices in the same year — e.g., for both president and Congress. In New Jersey, allies of Cory Booker, whose Senate seat is on the ballot in 2020, passed a law last year clarifying that it is legal to accept a presidential or vice-presidential nomination and still be on the ballot for another office in New Jersey. Booker hasn’t said whether he plans to run for re-election to the Senate, but he has said he’s “grateful … that that possibility is there.”

The quixotic presidential bids by sitting U.S. representatives also make a little bit more sense when you consider that most of them are free to run for re-election at the same time because of the laws of their home states. Tulsi Gabbard can run for president and the U.S. House in Hawaii. And Tim Ryan, who entered the presidential race in early April, has said previously that he planned to take advantage of the fact that Ohio does not prohibit him from running for president and Congress at the same time. The same is true in Massachusetts, which could explain why Seth Moulton is openly considering a presidential campaign as well.

But there are two unlucky candidates who would have been up for re-election in 2020 but are not allowed to run for multiple offices at once: Washington Gov. Jay Inslee and former U.S. Rep. John Delaney. However, even Inslee might not be giving anything up by throwing his hat in the ring. Washington’s filing deadline isn’t until May 15, 2020, after most presidential primaries and caucuses will have taken place. That means that Inslee will likely know before his state’s filing deadline whether he’s on track to win the Democratic presidential nomination. If he’s not, he could easily exit the presidential race and run for re-election to the governorship instead. Indeed, he’s not ruling out doing exactly that.

That leaves Delaney as the only 2020 Democrat who, to my eyes, is really putting his political career on the line to run for president. Maryland law prohibits individuals from being a candidate for more than one public office, which means that Delaney couldn’t run for both president and re-election to his House seat in 2020. (The Maryland filing deadline is Feb. 5, 2020; only one state — Iowa — will have held its presidential nominating contest by then.) In fact, Delaney has already crossed the Rubicon and given up his seat in Congress; he announced his presidential bid in July 2017 and forwent re-election in 2018 to commit to his White House bid.

Finally, there are a couple of cases where the answer to whether a candidate can keep his day job and still run for president is complicated. Under California law, Eric Swalwell might be able to run both for president and for re-election to his U.S. House seat, but the law is vague. Swalwell has gotten around the question by simply saying that he won’t try to run for re-election if he is still in the presidential race at the time of the California filing deadline. (Of course, he could decide to drop out of the presidential race before the filing deadline to run again for Congress.) And Pete Buttigieg’s obstacle is a logistical one, not a legal one. While Buttigieg could have run for re-election as South Bend mayor in November 2019 and then president in 2020, that would have either required him to campaign for both offices at once or to enter the presidential race extremely late. Practically speaking, he probably had no choice but to not seek a third term as mayor.

Still, the vast majority of Democratic candidates for president won’t have to give up their current job if they fail to win the nomination. This probably is one factor behind the massive size of the Democratic field, especially in the absence of a clear front-runner. However, it surely isn’t the only reason. After all, there are plenty of Democratic senators, House members and governors who could run for president without giving up their influential day job but are not. That reflects that there are some clear downsides to running for president, including the huge amount of work and the chance that a candidate’s reputation will come out worse, not better, in the end.

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