Senate Minority Leader Mitch McConnell formally endorsed Mitt Romney on Tuesday, saying the Republican Party is "behind him."

"I support Governor Romney for president of the United States and he is going to be the nominee," the Kentucky senator told reporters on Capitol Hill. "The party is in the process of unifying behind him and I think it's gonna be an incredibly close, hard-fought race."

His comments came hours after House Speaker John Boehner announced support for Romney, after largely staying out of the GOP presidential horse race.

"We're all behind (Romney) and looking forward to the fall campaign, which is actually already underway," McConnell said.

While McConnell had not officially supported Romney until Tuesday, he predicted earlier in the month on CNN's "State of the Union" that Romney would be an "excellent nominee."