Sam Brownback quit the Republican presidential race on Thursday, prompting a wave of speculation—perhaps the best press he earned all year?—about which of his foes he might throw his support to.

But that guessing game assumes that Mr. Brownback, who in polls was statistically indistinguishable from Duncan Hunter, had any meaningful support in the first place. Chances are his endorsement, if he ultimately offers one, will carry about as much weight as Al Haig’s did in 1988. (When the retired General dropped out and backed Bob Dole, the few voters who noticed were shocked…to learn that General Haig had been a candidate in the first place.)

Mr. Brownback’s departure does represent another step in the gradual thinning of the comically crowded G.O.P. race, a process that will accelerate in the coming months. As these candidates keel over on the side of the road, a more relevant question than whom they might support is whether we’ve seen the last of them on the presidential level.

After all, four of the last six G.O.P. standard-bearers had losing White House campaigns under their belts before finally securing the nomination. Mr. Brownback in particular ought to be encouraged by this: His fellow Kansan, Bob Dole, waged an epically miserable campaign in 1980, collecting a mere 608 votes in New Hampshire, only to end up winning the 1996 nomination.

Moreover, with the 2008 general election looking like a tough prospect for whichever nominee the party chooses, it’s worth asking which of the many Republican candidates might be able to take a mulligan and live to run again in 2012, when the fall playing field just might be more favorable.

Sam Brownback

Status: Just dropped out

Age: 51

Future prospects: This was probably it for him. The premise of Mr. Brownback’s candidacy was never that he’d win the nomination, just that he’d excite the party’s most passionate socially conservative elements. Had he at least managed to do that, there’d be no limit to the number of times he could run in the future (like Alan Keyes). But Mr. Brownback has been a dud on all levels. His target voters won’t be calling on him to run in the future, and neither will anyone else. But he’s young enough to serve in the Senate for many more decades – and blessed to live a state that will probably let him do just that if he so desires.

Jim Gilmore

Status: Already dropped out

Age: 58

Future prospects: OK, saying this guy “ran for President” in the first place may be stretching the term. Few people even knew he’d entered the race. He raised no money, garnered no support, and barely even campaigned, other than showing up at a few debates for his obligatory three minutes of camera time. He had no business ever entertaining a White House bid, and it’s unimaginable he’d ever do so again. But his political career isn’t quite dead: Mr. Gilmore, who served as Virginia’s governor for one rocky term a decade ago, is likely to run for the seat of retiring Senator John Warner. He might win his party’s nomination for Senate, but that’s as far as he’ll get, with Democrat Mark Warner, who leads his likely G.O.P. opponents by more than 30 points in polls, waiting in the fall.

Duncan Hunter

Status: Next to go?

Age: 59

Future prospects: He’s only running because he was looking to escape the U.S. House (where he’s served since 1980) and figured the unparalleled exposure of a presidential campaign – even on a shoestring budget – would make it more likely that his son will replace him in Congress next year. Think that sounds too cynical? Next time you listen to Mr. Hunter, count how many seconds it takes him to mention Iraq and the fact that his son is stationed there. Then ask yourself when the last time John McCain drew similar attention to his own son, who is also in Iraq. (The answer is never.) Mr. Hunter won’t have any plausible options in electoral politics after this race. He is one of 53 Congressmen in California, which puts him in terrible position if he has any thoughts of statewide office. And even if his son doesn’t win the Congressional race, Mr. Hunter’s seat will stay in G.O.P. hands, meaning there won’t be any comeback by the elder Hunter in 2010. A lucrative lobbying career sounds about right for the soon-to-be former Congressman.

Tom Tancredo

Status: Still running (I think)

Age: 61

Future prospects: He is running as a “cause” candidate (illegal immigration, if you haven’t heard), so theoretically we could see him carrying the same banner in a future national campaign. But so far, he’s gained little traction and largely blended in with the rest of the field. He could end up as the G.O.P.’s Kucinich – an otherwise obscure Congressman with a small but committed single-issue following who loves being on stage with his party’s national heavyweights. But if Mr. Tancredo finds himself with such temptations in 2012, he should be careful: Mr. Kucinich is learning that his Ohio Congressional constituents are quickly tiring of his national campaign and may throw him out in next year’s Democratic primary. Mr. Tancredo might also run for statewide office in Colorado, where he has considerable name recognition (a mixed blessing, given his polarizing message) and where Republicans can still compete.

Ron Paul

Status: Still raising hell…and lots of money too

Age: 72

Future prospects: At his age, it’s tempting to say this is Dr. Paul’s last shot, no matter what. Then again, Mike Gravel is 77 and has still managed to finagle an invite to almost every Democratic debate. And given the devotion of Dr. Paul’s flock, there’s no reason he wouldn’t be able to raise some real money in 2012, even if the media initially decided to give him the cold shoulder. He is the ultimate “cause” candidate, preaching a philosophy without a real shelf life. Right now, no one knows quite what to make of his ’08 effort: He won’t win (right?), but it’s not unthinkable that he might crack double-digits in some early states. The more surprising his showing, the more his supports will agitate for a follow-up run in 2012 – and the tougher it will be for the media and party leadership to deny him a seat at the table. Unless, of course, he winds up bolting the G.O.P. for a third-party bid.

Mike Huckabee

Status: Very much alive

Age: 53

Future prospects: Of all the Republicans now running, Mr. Huckabee is best positioned for a second try in 2012. He has won positive reviews from the media and activists alike for his warm, personable style, not to mention the supremely effective preacher’s touch he brings to his stump speeches and debate performances. So far, he’s made the most of his opportunity this year, and while he hasn’t raised much money, he’s now running in a tie for second place in Iowa. There’s a remote chance Mr. Huckabee could win Iowa and catapult to the front of the pack, but more likely he’ll settle for a “better than expected” showing in Iowa and South Carolina, gracefully bow out and endorse the G.O.P. nominee – and immediately begin running again on November 5, 2008. He could also pursue a future Senate opening in Arkansas, but that wouldn’t get him any closer to the presidency than he is now. It should also be noted that Mr. Huckabee is not an implausible V.P. pick for next year, which would be the optimal springboard to another run for the top job.

John McCain

Status: Broke but still running

Age: 71, or “older than dirt” (but younger than Ron Paul)

Future prospects: He campaigned with his spry 95-year-old mother this week, so genetics would suggest that the septuagenarian Mr. McCain has plenty of years ahead of him. But his second presidential bid will clearly be his last, barring a miraculous chain of events that lead to a McCain re-election campaign in 2012. Interestingly, Mr. McCain’s ’08 effort was initially inspired by his party’s tendency to nominate the previous runner-up. But Mr. McCain, unlike Bob Dole, George H.W. Bush and Ronald Regan before him, found the transition from insurgent to establishment front-runner impossible to make. Now he’s (more or less) back to his maverick ways, so if he does go down in his last White House campaign, at least he’ll do it on his own terms.

Mitt Romney

Status: In the mix

Age: 60

Future prospects: Next to Mr. Huckabee (and maybe Dr. Paul), Mr. Romney is probably the next most likely Republican to try again in the future. He looks much younger than his 60 years and has assembled an impressive political organization and strong support in most early states. The problem is that he may have peaked too soon. Instead of gradually building support, Mr. Romney rocketed to the top of polls in Iowa and New Hampshire months ago, and he’s now the undisputed front-runner in both states. Nothing wrong with that, but if Mr. Romney does fall short this time around (which seems increasingly likely) it might be considered a “bad” loss. In other words, if he fares poorly in Iowa and New Hampshire after leading in the polls for so long, opinion-makers in the media and G.O.P. could conclude that Mr. Romney is a fatally flawed candidate who doesn’t wear well on an electorate, a perception that could prevent him from getting off the ground in 2012. To be viable for the future, he needs to win some states in 2008. Mr. Romney has no electoral options beyond the presidency, having alienated the vast majority of Massachusetts voters. (A shocking poll a few weeks ago found him losing to Hillary Clinton in Massachusetts – among pro-life voters.)

Fred Thompson

Status: Still running…and still waiting for applause

Age: 65

Future prospects: He has none, unless he cuts back on the sleeping pills and rescues his current campaign. Mr. Thompson is only running because he was drafted into the race by a mix of activists, money men (and women), and establishment Republicans who decided he was the savior he would ignite the party base, win over independents and rescue the White House for the G.O.P. But he’s been a dud. The bar was set very high for Mr. Thompson – with good reason – and anything short of victory next year will be a huge let-down for those who begged him to run. Right now, it looks like he’ll fall well short. We won’t have Fred Thompson to kick around in 2012.

Rudy Giuliani

Status: The man to beat

Age: 63

Future prospects: This is it. The good news for Rudy is that he is well positioned to win the G.O.P. nomination, and he probably has the best chance of any Republican of winning in the fall. Mr. Giuliani’s vulnerabilities with the right on social issues have been over-dramatized, but it is obviously unusual for the G.O.P. to rally around someone with his profile. If he can’t win the nomination in 2008, his position within the party will only weaken in the run-up to ’12, with social conservative leaders saying “I told you so” and the memory of his 9/11 role only fading from people’s minds. If it’s going to happen for Rudy Giuliani, 2008 is the year.

Of course, if he were to win the nomination and lose an excruciatingly close and controversial general election to Hillary Clinton, he could potentially rally the G.O.P. around him for a rematch in 2012. But that is the only scenario where a vanquished Rudy might be nationally viable after 2008.