With four weeks to go, President Barack Obama, Mitt Romney revisit Ohio

COLUMBUS, Ohio - Ohio again takes center stage in the presidential race as President Barack Obama and Republican candidate Mitt Romney return to the swing state.

   The Democratic president was scheduled to speak to a crowd on the Ohio State University campus Tuesday evening. The event was expected to include a performance by will.i.am of the Black Eyed Peas.

   Romney was scheduled to spend the evening in northeast Ohio, joining New Jersey Gov. Chris Christie at a rally in Cuyahoga Falls. It's one of several expected Ohio stops for the Republican this week.

   Tuesday's visits come on the final day of voter registration in Ohio.

   In a sign of its importance, the two campaigns and their outside supporters have spent more than $110 million on TV advertising in the perennial battleground state.