TALLAHASSEE, Fla. -

U.S. Sen. Bill Nelson is raising far more money than his opponent in his re-election campaign, but he still could be outspent in his bid for a third term.

Nelson's campaign raised $1.8 million in the second quarter of the year that ended June 30. The campaign has $11 million cash on hand.

Republican U.S. Rep. Connie Mack's campaign reported raising $839,556 during the quarter and having $1.35 million cash on hand.

Nelson is being targeted by conservative super PACS that already have spent millions of dollars on ads against the Democrat. Many of the ads are paid for by undisclosed donors.

The Nelson campaign said Wednesday that Karl Rove's American Crossroads organization has reserved $6.2 million for airtime in Florida for attack ads against Nelson.