With 100 days until the 2012 election, President Obama has a tenuous lead, but the struggling economy hurts his bid for a second term.

Obama leads Mitt Romney by a narrow margin in most national polls, and has a slightly wider lead in most swing states, giving Romney little room for error. But while Obama continues to lead Romney in personal likability — a major asset — there are few signs that Obama’s sustained summer attack on Romney’s business background has changed the contours of the race.

The president, Romney and their allies have spent hundreds of millions of dollars on advertising since the general election campaign officially began, though neither side has been able to move the needle much.