GREAT FALLS, Mont. (AP) — U.S. Sen. John McCain says the balance of the U.S. Senate "to a large degree" depends on Montana's race.

McCain appeared Friday in Great Falls to support U.S. Rep. Denny Rehberg in his bid to unseat U.S. Sen. Jon Tester. He said there's "no doubt" in his mind it will be a very close race that could decide whether Republicans win control of the chamber.

Rehberg and McCain blamed the Obama administration for pending defense cuts that came out of bipartisan deficit reduction talks as Rehberg looked to woo veterans who are perceived to be a strength for Tester.

McCain also made clear he fully supports Rehberg, although the two Republicans may disagree on the U.S. Supreme Court's Citizen's United campaign finance decision.

The Arizona lawmaker's comments came after Tester ran an ad in the Great Falls Tribune thanking McCain for opposing the decision, which Rehberg supported.