HOLLYWOOD, Fla. (AP) — Two days from judgment by the voters, President Barack Obama raced through four far-flung battleground states on Sunday while Mitt Romney ventured into traditionally Democratic Pennsylvania, seeking a breakthrough in a close race he mused aloud he might lose.

Appearing before some of the largest crowds of the campaign, the two rivals stressed their differences on the economy, health care and more while professing an eagerness to work across party lines and end gridlock in Washington.

"You have the power," Obama, the most powerful political leader in the world, told thousands of cheering supporters in New Hampshire, his first appearance of a day not scheduled to end until after midnight in the East.

Later, in Cleveland, boos from Romney's partisans turned to appreciative laughter when the Republican nominee began a sentence by saying, "If the president were to be elected," and ended it with, "It's possible but not likely." It was a rare public acknowledgement that despite expressions of confidence from him and his aides, defeat was a possibility.

In a campaign that began more than a year ago, late public opinion polls were unpredictably tight for the nationwide popular vote. But they suggested at least a slim advantage for the president in the state-by-state competition for electoral votes that will settle the contest, including Ohio, Wisconsin, Iowa and Nevada.