DENVER — Now in the presidential campaign’s final two weeks, President Barack 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.

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.”