Which presidential candidate will quit first?

Seventeen Republican and five Democrats are running for president. So who drops out first?

All 22 candidates are accomplished careerists who hold, or have held, important jobs: There are eleven governors, nine U.S. senators, a U.S. secretary of state, a Fortune 500 CEO, a noted billionaire and a preeminent neurosurgeon. All have big egos and none like to lose. But the inevitable winnowing process will occur and most of them won’t make it.

{mosads}While there is good reason for candidates to hit the exit door before their prospects go from bad to worse to humiliation, two things may keep Republican underdogs in the race. First, there is the unusually large field. Anybody who can piece together a measly 15 percent of the vote in a primary may win it, or at least come close. Second, cash-flush super-PACs may serve as respirators, breathing temporary life into dying campaigns that should be allowed to mercifully fade away.

Post-election career prospects may also play a role. Which of today’s candidates are angling to be vice president, a Cabinet member or an ambassador? Which ones want to start advocacy groups, think tanks or host TV shows? Which ones intend to cash in on newfound fame by fattening up speaking fees and book royalties? These considerations, sometimes as much or more than actually getting elected, can shape presidential candidate behavior.

Contenders with money or momentum are not likely to be contemplating withdrawal any time soon. They’re busy scheming to win. But a few others may sooner, rather than later, start looking for an out.

Former Texas Gov. Rick Perry (R) is one such possibility. His campaign has failed to launch. Relegated to the junior-varsity debate, he is having trouble raising money and has stopped paying staff. His super-PAC may try to rescue his chances, but Perry’s not the kind of guy who wants to take another public beating. He could go first.

Former Sen. Rick Santorum (R-Pa.) had his moment in the sun when he won 11 states in his 2012 nomination quest, including Iowa, drawing heavily on an evangelical base. But this time, that base is splintered. Santorum knows what it’s like to be an underdog who catches fire. He also knows what it’s like to lose in the end. A recent poll showed him running ninth in his home state of Pennsylvania. He may decide that withdrawal is the better part of valor.

Another contender for early withdrawal may be, surprisingly, Sen. Rand Paul (R-Ky.), who was once crowned a top contender by the media. His poll numbers are down and his debate performance didn’t help. More importantly, his Senate seat is also on the ballot in 2016. At some point, he may decide to go home.

Gov. Chris Christie (R-N.J.) and former Govs. George Pataki (R-N.Y.) and Jim Gilmore (R-Va.) are serious people who are not being taken seriously as presidential aspirants. Running last or near last in a primary is an adventure that is best avoided, especially if you’ve once tasted genuine victory, as they all have. Getting out early may be their best bet.

Of course, there’s the matter of Donald Trump. If his momentum fades, will he stay in the race and wait until the national convention to take his final bow? Or will he get mad, pull a Ross Perot, and abruptly quit? The only rational answer is a question: Who knows? For now, the last thing on Trump’s mind is getting out.

On the Democratic side, everybody’s waiting to see if one of Hillary Clinton’s controversies turns out to be a full-fledged scandal that opens up new paths for long shots and even new entrants. A Clinton implosion may never happen — but that it could will keep the melodious strings of “Hail to the Chief” playing in the heads of ambitious Democrats who, perhaps, should be listening to adult contemporary music instead.

Faucheux is president of Clarus Research Group, a nonpartisan polling firm based in Washington. He also publishes LunchtimePolitics.com, a daily newsletter about polls and public opinion trends.