Sen. Sherrod Brown (D-Ohio) raised $1.3 million in the first quarter of the year ahead of what could be a tough race for reelection.

Brown is sitting on $2.5 million cash on hand, according to the Cleveland Plain Dealer.

It's a solid fundraising start for Brown, whom national Republicans claim is a top 2012 target. But the GOP is still searching for a challenger to run against the first-term senator. A handful of GOP members of the state's congressional delegation are rumored hopefuls, as is Ohio state Treasurer Josh Mandel.

A recent survey from Democratic-leaning Public Policy Polling found Brown leading all potential GOP opponents by double digits.