Some people run for president to raise their national profile. In Rep. Seth Moulton’s case, his campaign didn’t even do that. Only 28 percent of Democrats could form an opinion of Moulton in an average of polls conducted between Aug. 1 and 20. This was lower name recognition than any of the other major presidential candidates in that time period and was a big part of the reason why Moulton never reached 2 percent in any poll — let alone one that counted toward debate qualification.

Moulton found himself stuck in a vicious cycle: Without higher polling numbers, he couldn’t qualify for the primary debates … and without being in the debates, he lacked a platform from which to improve his polling numbers. So on Friday, the Massachusetts congressman dropped out of the Democratic primary for president in a speech to the Democratic National Committee. He is the fifth candidate to drop out this summer and the third in just the past nine days. His departure leaves us with 20 major Democratic candidates for president, by FiveThirtyEight’s definition.

A Marine veteran who served four tours in Iraq, Moulton focused his campaign on national security and veterans’ issues; the most memorable moment of his campaign was probably his poignant admission that he had sought treatment for post-traumatic stress. But polls showed that foreign policy is not a top priority for voters (and hasn’t been for the past several cycles), and our research last year suggested that candidates who are veterans don’t win Democratic primaries at higher rates.

Moulton’s path was also blocked by higher-profile candidates who appealed to the same constituencies. If voters were looking for a Harvard-educated veteran around 40 years of age, they already had South Bend, Indiana, Mayor Pete Buttigieg, whose polling surge came just before Moulton entered the race. Indeed, Moulton admitted to The New York Times that he had made a mistake with his late announcement date, which gave him just seven weeks to collect the necessary polls or donors to qualify for the first debate. And if voters were looking for someone “electable” or who didn’t hail from the progressive wing of the party, there was former Vice President Joe Biden, who has dominated polls among those whose first priority is defeating President Trump and among moderate and conservative Democrats. Moulton praised Biden upon his exit from the race, although he stopped short of a formal endorsement: “I think it’s evident that this is now a three-way race between Biden, [Sen. Elizabeth] Warren and [Sen. Bernie] Sanders, and really it’s a debate about how far left the party should go,” he told the Times. “I’m not going to endorse anyone right away, but the vice president is a mentor and a friend and I think he’d make a great president.”

Other than financial difficulties (he reportedly had to lay off many of his staffers earlier this month), one other factor may explain why Moulton dropped out so early: The clock was ticking on his decision to run for another office. In this respect, Moulton fits into a clear pattern of those who have dropped out of the race so far. Rep. Eric Swalwell and Washington Gov. Jay Inslee would have encountered legal issues if they tried to run for president and for reelection at the same time, and when their presidential campaigns failed to catch fire, they took the safer route and chose to hold onto their day jobs. Former Colorado Gov. John Hickenlooper, meanwhile, faced intense pressure to run for a Republican-held Senate seat, which he finally decided to do this week. And while Moulton could have legally run for president and the House at the same time, he is already facing a couple of primary challenges in the Massachusetts 6th District, and the longer his attention was elsewhere, the more vulnerable he probably would have been back home. Moulton confirmed on Friday that he would seek reelection, trading one contested primary for another — though his chances of winning the new one are much higher.