By Sam Youngman and Jeff Mason
CINCINNATI/CHICAGO (Reuters) - He does it too often to be a slip of the tongue.
When Republican presidential candidate Mitt Romney addresses his growing crowds, he always catches himself.
"If I'm president - when, I'm president," Romney says in his speeches now, drawing cheers from the crowd.
Polls suggest Democratic President Barack Obama retains a tenuous hold on the handful of states that will decide the race for the White House, but Romney is casting himself as the man with momentum, rolling toward an inevitable victory on November 6.
Three weeks after Romney's solid performance in his first televised debate against Obama allowed him to chip away at the incumbent's lead in the polls, Romney's strategy appears to boil down to this: to become president, you must act like one.
So Romney, at a brief stop in Cedar Rapids, Iowa, on Wednesday night, said flatly: "We're going to win."
And in Worthington, Ohio, on Thursday, he told supporters: "I want you to know how optimistic I am. This is about to get real good."
Analysts and Republican strategists are praising the tactic, noting that a key element of winning undecided voters is to convince them that they're on a winning team.
"He wants to be seen as the projected winner to get those few undecideds in key states to feel that a vote for Romney is for the next president of the United States," said Larry Berman, a political science professor at Georgia State University.
Obama campaign advisers say that the Romney team is trying to create a false sense of momentum.
They acknowledge the challenger's bounce from the first presidential debate, but say that Obama got the better of the former Massachusetts governor in their other two debates, and say that the electoral numbers favor an Obama victory.
'WE PULLED AN ALL-NIGHTER!'
Obama, whose successful run for the White House in 2008 was cloaked in the slogans "Hope" and "Change," is taking an edgier approach in the final days of this campaign as he tries to show that he has the momentum.
The president is striking an optimistic tone, but he also is blasting Romney as a disingenuous candidate who changes positions to try to fool voters.
Obama aides and outside analysts point to a projected lead in the electoral college, early voting statistics that favor Democrats, and volunteer enthusiasm in the president's massive get-out-the-vote operation as evidence of Obama's momentum.
The president has drawn large crowds during a two-day, eight-state tour that has taken him to Iowa, Colorado, Nevada, Florida, Ohio, Virginia, California and Illinois.
The campaign said that 8,500 people showed up for an early morning rally in Tampa, Florida, on Thursday and about 15,000 were at one in Richmond, Virginia.
"We are right in the middle of our 48-hour, fly-around campaign extravaganza," he said to applause in Florida. "We pulled an all-nighter last night!"
On Thursday, Obama picked up the endorsement of former Secretary of State Colin Powell, a Republican who also endorsed him in 2008, as well as that of The Washington Post, which could help him in the northern Virginia suburbs of Washington, a key area in Obama's push to win politically divided Virginia.
'EVERYONE LIKES A WINNER'
Romney's closing strategy was clear in a fundraising e-mail his campaign sent Thursday morning. The subject line read, "The momentum."
"The debates have supercharged our campaign. We're seeing more and more enthusiasm - and more and more support," Romney said in the e-mail. "This has become more than just a campaign. It's become a national movement. Americans recognize we can do better as a nation than we've done over these last four years."
Republican strategist Rob Johnson, who managed Texas Governor Rick Perry's unsuccessful run for the 2012 Republican presidential nomination, praised the strategy.
"Everyone likes a winner, and (Romney) is showing himself to be just that with his positive vision for America," Johnson said.
Republicans and Romney campaign officials say that opinion polls and bigger crowds are only partial evidence that the race is turning in Romney's favor.
The real proof, they say, is Obama's sharp attacks on the Republican. Romney aides say Obama is acting like a desperate candidate.
"The Obama campaign is slipping," Romney said in Ohio on Thursday, "because they're talking about smaller and smaller things."
(Editing by David Lindsey and Paul Simao)