Wealthy car dealer Tom Ganley (R) is dropping out of the open-seat Ohio Senate race and will challenge Rep. Betty Sutton (D) in the 13th district instead, according to a source familiar with the decision.

The Ganley switch is a coup for Republicans because it gives former Rep. Rob Portman a clear path to the GOP Senate nomination and could put another Democratic-held House seat into play. A recent internal GOP poll showed Ganley leading Sutton by 3 points.

Portman can now save his campaign war chest — he had $6 million on hand as of Dec. 31 — for the general election race against Lt. Gov. Lee Fisher, the likely Democratic nominee, instead of spending heavily in the May 4 primary. Ganley had invested $1.6 million of his own money in the Senate race and was already airing television ads.

Now, Ganley can convert the almost $1.3 million in his Senate campaign account to a House account, giving him a large early cash advantage over Sutton, who had only $210,000 at the end of last year.

Sutton won the 2006 open-seat race to replace now-Sen. Sherrod Brown (D) with 61 percent of the vote. She was re-elected easily in 2008 with 65 percent. President Barack Obama won Sutton’s district easily in 2008 by 15 points, but Republican insiders believe Ganley will instantly turn this into a competitive contest.