Former Rep. Rob Portman (R) kicked off his 2010 campaign to succeed retiring Sen. George Voinovich (R) on Wednesday in Southern Ohio, and Buckeye State Republicans on Capitol Hill quickly began coalescing behind his candidacy.

In the wake of Voinovich’s retirement announcement earlier this week, Portman was widely viewed as the GOP’s best hope to retain control of the seat in 2010. Minority Leader John Boehner (R) and GOP Reps. Jean Schmidt and Bob Latta all endorsed Portman on Wednesday.

Portman made his candidacy official at a restaurant in Lebanon, Ohio — the first stop of a five-city statewide tour to promote his campaign. Portman stopped in Toledo on Wednesday and is scheduled to be in Cleveland, Columbus and Cincinnati today.

“My heart is in public service,” Portman said in a statement on his campaign Web site. “Just as it was an honor to serve the people of Southern Ohio in the U.S. House of Representatives for 12 years, so it would be an honor to serve all Ohioans in the U.S. Senate.”

Lt. Gov. Lee Fisher and Reps. Tim Ryan, Zack Space and Betty Sutton are all mentioned as possible Democratic candidates.