DENVER – Now in the presidential campaign’s final two weeks, President Obama and Republican Mitt Romney crisscrossed the nation Wednesday in search of support from the remaining undecided voters in swing states who will determine the next occupant of the White House.

Romney, appearing in Reno, Nev., declared that a trio of presidential debates left Obama’s campaign “slipping and shrinking.” He exuded confidence, twice correcting himself, replacing “If I’m elected,” with “No, when I’m elected.”

“We’ve had a number of debates lately, did you notice that? And they have really propelled our campaign,” he said. “We’ve seen that across the country — and at the same time I think in some respects they’ve diminished the president’s campaign because he’s now been reduced to talking about Sesame Street characters, word games and misplaced attacks on me.”

Obama embarked on a marathon tour of a half-dozen battleground states Wednesday, attempting to chip away at Romney’s apparent momentum. He flew from coast to coast with stops in Iowa, Colorado and Nevada on Wednesday and Florida, Virginia and Ohio on Thursday.

He also stopped Wednesday in California to tape an appearance on “The Tonight Show with Jay Leno.” While traveling on Air Force One, he made calls to undecided voters and to 50 disc jockeys, most of them African-American, in swing states.

Obama continued to criticize Romney for flip-flopping on issues — which he has dubbed “Romnesia” — but returned to a familiar plea for voters to give him the time he needs to finish his goals.

“We haven’t finished everything that we want to get done,” he said. “That’s why I’m running for a second term.”

Romney has an edge in national rankings, according to a compilation of surveys by the website RealClearPolitics, although Obama continues to lead in some battleground states, including Ohio, New Hampshire and Iowa.