There are seven days until early voting begins in Iowa, less than two weeks until the first debate and 46 days left in the race for Mitt Romney to change the dynamic of a campaign that by many indicators is tilting against him.

That, advisers to President Obama acknowledge, is plenty of time.

But the burden rests to a remarkable degree directly on Mr. Romney and his ability to restore confidence to his campaign, become a more nimble candidate and clearly explain to voters why he would be the better choice to repair the economy and lead the nation in addressing its challenges at home and abroad.