DES MOINES, Iowa (AP) — In a presidential race seemingly frozen in place for months, the advantage has shifted toward President Barack Obama.

That change follows a series of miscues by Mitt Romney, punctuated by the Republican challenger's comments about people who pay no income tax.

Despite a continuing gray economic sky and unrest in the Mideast, the president has edged ahead of Romney in some of the most competitive states, including Iowa and Virginia, and forced Romney to redouble efforts in Florida and Ohio — which he probably must win if he wants to be president.

With about six weeks left before Election Day and early voting under way in some states, Romney faces a problematic map, a ticking clock and a campaign demeanor that has failed to click with many voters.