Rep. Dan Benishek, R-Mich., raised $487,000 in the second quarter, a sharp increase from his haul during the first three months of the year.
The second-term Republican, a top Democratic target, had $942,000 in cash on hand as of June 30, according to figures provided first to CQ Roll Call.
Benishek, who had raised just $145,000 in the first quarter, is being challenged by Jerry Cannon, a veteran and former sheriff whom Democrats are counting on to put the 1st District in play.
Cannon has yet to release his second-quarter figures. He ended March with $270,000 in cash on hand.
After winning the Upper Pensinsula-based open seat in 2010, Benishek eked out a rematch win over his Democratic opponent in 2012 by fewer than 2,000 votes — even as Mitt Romney carried it by an 8-point margin.
The Democratic Congressional Campaign Committee has reserved more than $1 million of airtime for the fall so far, signaling they are gearing up for a competitive race.
Michigan's 1st District is rated Tilts Republican by Rothenberg Political Report/Roll Call.