Last week, the New York Times surveyed an “anxious Democratic Establishment” and found people casting about for new presidential candidates, and some prospective candidates giving a late entry into the race at least of modicum of thought.

Former Secretaries of State Hillary Clinton and John Kerry, former New York City Mayor Michael Bloomberg, former Attorney General Eric Holder, former Massachusetts Gov. Deval Patrick and Sen. Sherrod Brown of Ohio have all apparently been approached by insiders or have otherwise considered jumping in.

These musings may not be, and probably are not, very serious. But if anyone on the sidelines is truly planning a last-minute attempt to shake up the primary, they should recognize that the track record of late entrants is atrocious.

In September 2003, some Democrats were briefly thrilled to see former NATO Commander Wesley Clark, who opposed the still-raging Iraq War, enter the race. They worried that the hot antiwar candidate of the summer, former Vermont Gov. Howard Dean, didn’t have a strong enough resume or stump discipline to challenge an incumbent wartime president. Even the filmmaker Michael Moore, then one of the most influential progressive figures, looked past Dean and long-shot lefties Rep. Dennis Kucinich and the Rev. Al Sharpton to publicly urge Clark to run, and once Clark obliged, gave him a formal endorsement.

But the day after Clark became a candidate, he bobbled the question of whether he would have voted for the congressional resolution that authorized military action in Iraq: “I don't know if I would have or not. I've said it both ways because when you get into this, what happens is you have to put yourself in a position -- on balance, I probably would have voted for it.” While the initial media frenzy had shot him to the top of the national polls, he quickly fell out of first place and never got a toehold in the early states.

Four years later, former Sen. (and movie star) Fred Dalton Thompson was the dream candidate of conservatives who saw in him a folksy, southern Ronald Reagan. He sought to leapfrog ahead of the Republican primary pack by biding his time until September, announcing his candidacy in glitzy, Hollywood style on “The Tonight Show.”

He got an announcement bounce in the polls and even led in a few, but it wasn’t long before his stump style was widely seen as less folksy and more lazy. Within weeks, he was skewered by comedian Darrell Hammond in a devastating “Saturday Night Live” impersonation: “I’m not saying that I don’t want to be your president, because I kinda do. … It’s just, how do you campaign when you don’t like hard work and people make you sick?” He managed to eke out a third-place showing in Iowa, but barely registered in New Hampshire and he quit soon after.

Perhaps the most comical late entry flameout was by then-Texas Gov. (now Secretary of Energy) Rick Perry. In August 2011, with conservatives yet again lamenting the ideological bona fides of the early GOP front-runner, Perry stormed into the race, suggesting President Obama didn’t love America and warning the Federal Reserve chairman it would be “almost treacherous, treasonous” if he moved to increase the money supply before the election. Perry’s take-no-prisoners approach rocketed him into the lead. One late August poll had him up 19 points. Then the debates came.

In a September debate, under fire from his Republican rivals, Perry struggled to explain his position on Social Security, his admittance of undocumented immigrant children to public colleges, and his decision as governor requiring sixth-grade girls to be vaccinated against human papilloma virus. Soon after, his polling lead vanished. By the time he blurted out his infamous “Oops” in a November debate, he had already sunk to single digits in some polls.

These three examples have a common theme. Late candidacies, almost by definition, begin with enormous hype. If that hype isn’t instantly met with an exceptional performance, the poll bubble bursts. There’s no time to iron out kinks and shake off rust. There’s no margin for error.

Candidates that start earlier, in contrast, have time to overcome mistakes and turn the page on past embarrassments. In the current presidential primary, Elizabeth Warren apologized for identifying herself as an “American Indian” back in February. At the time it seemed like the lingering controversy about her ancestry was going to stifle her campaign before it could get off the ground. Today, several white papers later, the matter rarely comes up (at least, among Democrats). Similarly, Joe Biden has been able to move past his controversial comments in June about working alongside segregationist senators during his early career.

Party loyalists can get anxious around the midway point of the primary season because presidential candidates are flawed human beings, and the harsh spotlight of the campaign trail exposes those imperfections. Even today, when the Democratic leaders all consistently beat President Trump in trial-heat polls, seeing those candidates perform inconsistently on the stump, take policy positions that carry general election risk, or awkwardly shift on issues out of political calculation, stirs up worries that the polls will shift for the worse in the fall of next year. Candidates on the sidelines, who have yet to go through the wringer, will always look shiny by comparison … until they get off the sidelines.

Late entries are bound to receive a crush of attention, and unless they perform to perfection, they will be crushed by that attention. Anxious Democrats, keep that mind, and get used to your imperfect field.