COLUMBUS, Ohio (AP) -- Democrat Sherrod Brown has won re-election to the U.S. Senate after one of the most expensive and closely watched match-ups in the country.

The 59-year-old Brown beat Republican challenger Josh Mandel despite an onslaught of attacks from conservative outside groups. Mandel is the state treasurer and a Marine veteran.

The U.S. Chamber of Commerce, Crossroads GPS and other outside groups spent more in Ohio than any other state, criticizing Brown's support for President Barack Obama's stimulus and health care overhaul.

Mandel called Brown a career politician, seeking to turn his decades in office against him. Mandel told voters he would make Washington more accountable.

Brown made the auto industry bailout a key campaign issue, highlighting Mandel's opposition to the rescue that affected about 800,000 Ohio jobs.