Presidential politics rises floodlike after Labor Day, and this month begins a Niagara of debates. Before long the airwaves of Des Moines, Iowa, and Manchester, N.H., will be full of appeals to voters and the papers will be full of poll figures.

One of those polls stuck out last week. It was the CNN weekly survey, and it showed that in less than three weeks, Gov. Rick Perry of Texas went from a statistical dead heat with Gov. Mitt Romney of Massachusetts to doubling Romney’s support, becoming the clear front-runner in the Republican race. That prompted a CNN commentary setting out a scenario for Campaign 2012 that would have been inconceivable on Independence Day:

If it was January/February 2012, Romney would win New Hampshire’s primary, while Perry would win the Iowa and Nevada caucuses and would take the South Carolina primary. Perry would then go into Super Tuesday the front-runner and would likely secure enough delegates in those contests to be the nominee. There is plenty of campaign to go, but that is how this race looks from Labor Day 2011.

But here is what could happen between Labor Day and the Republican National Convention in Tampa 51 weeks from now:

Nothing

This is not likely but possible. The prognosis above is plausible. Perry is strongly positioned to win the Iowa caucuses. He packs the evangelical and stylistic punch to prevail in a state that in the past quarter-century has seen abortion politics and social conservatism dominate the Republican debate.

If Perry does prevail in Iowa, he’s not likely to win in New Hampshire, the next contest. That’s because New Hampshire often acts as an antidote to Iowa; former Gov. Mike Huckabee of Arkansas was the GOP winner in Iowa four years ago but lost to Romney in New Hampshire, just as Sen. Barack Obama of Illinois was the Democratic winner in Iowa but lost New Hampshire to Sen. Hillary Rodham Clinton of New York.

This pattern has historical roots. In 1988, Sen. Bob Dole of Kansas won Iowa but lost New Hampshire to Vice President George H.W. Bush. And all this is without considering how hostile the terrain of New Hampshire likely will be to Perry. The state has little religious-conservative fervor and, more important, invites independents (who are unlikely to be Perry supporters) to vote in its primary.

The rest of the CNN scenario could happen. Romney as a Mormon has a fighting chance in Nevada but not much of one in South Carolina, unless former Sen. Rick Santorum of Pennsylvania and Rep. Michele Bachmann of Minnesota remain in the race that long, dividing the social-conservative vote and providing a surprising sunny opening for Romney. If not, Perry could be home free.

Perry stumbles

Part of the Texas governor’s special appeal is his candor. He’s not one of those candidates who try to say what you think. He says what he thinks, and that formula has worked for him.

Unlike Romney, who lost a Senate race to Edward M. Kennedy in Massachusetts and a presidential nomination fight to Sen. John McCain of Arizona, Perry has never lost an election. Caveat: Though he defeated the popular Sen. Kay Bailey Hutchison in a bruising gubernatorial primary last year, Perry hasn’t faced competition nearly as formidable as Romney has.

Perry’s campaign depends in unusual measure on his candor. If he transforms it into charm, he could be on the way to the nomination. If he transforms it into recklessness, he could be roadkill.

Romney surges or endures

Romney is more sure-footed than Perry and probably will continue to be better funded than his Texas rival. He won’t lose his temper or his focus. The Republican Old Guard isn’t nearly as potent as it once was, but it doesn’t want Perry at the top of the ticket and will do everything it can to derail him.

The Republican instinct to pick the Next Guy isn’t nearly as strong as it once was, either, but Romney is indisputably the Next Guy and could be the man left standing after everyone else has run of money and the public has run out of patience.

Don’t count him out. The Don’t-Underestimate-Him candidate is said to be Perry, but Romney has a claim to the title as well; hardly anyone’s passionate about him, yet he’s still around. He wants it more than Perry, is more disciplined and has prepared longer and more deeply. Florida, the first place where there is no natural advantage for any candidate, could be a crucial test. Romney is readier there in September than Perry will be in March.

Someone else emerges

The hope that someone else may join the field dwindles with every day, though do not forget how late (March 16) Robert F. Kennedy joined the Democratic contest in 1968 — and he very well might have won the nomination had he not been murdered.

The 2012 GOP nomination remains a glittery prize; it isn’t every day you can run against an incumbent whose disapproval rating is 60 percent (Zogby International) at a time when most likely voters say it’s time for someone new in the presidency (55 percent, Zogby) and when consumer confidence has hit a two-year low. A new entrant could change everything. Then again, maybe the new entrant already has entered. His name is Rick Perry.

Some event intercedes

Mayor Joseph B. Harrington of Salem, Mass., was an America-First candidate in a special congressional election on Boston’s North Shore, a Democrat who had distanced himself from Franklin Roosevelt and proclaimed himself “100 percent opposed to President Roosevelt’s foreign policy.” He almost certainly would have won the seat but for one thing. The primary was on Dec. 16, 1941.

Events matter, and the unpredictable is, by definition, difficult to imagine. Perry is in a strong position on the eve of Labor Day. But CNN is right. There is plenty of campaign to go.