Sen. John McCain (R-Ariz.) headlined two campaign rallies for Colorado Senate candidate Jane Norton (R) Sunday.

Norton is locked in a close and nasty primary battle with prosecutor Ken Buck (R). The state's primary is Tuesday. 

McCain steered clear of trashing Buck directly Sunday, but did reference Norton's rival at a stop in Grand Junction when he implored the crowd to help get out the vote on primary day to ensure "the Buck stops here."

McCain predicted that Republicans would take back the Senate in January, and said Norton would be a new leader for the party in the upper chamber. 

"We'll repeal and replace Obamacare and stop this massive takeover of healthcare by the federal government," McCain said.

Norton, who has tried to run from the establishment label her primary opponent has tagged her with, stressed that she won't agree with McCain on every issue but called him "an American hero."

Buck has dismissed Norton's endorsement from McCain, calling her the senator's "hand-picked candidate." 

No matter who wins Tuesday's primary, Democrats in the state say the nominee will have a tough time winning over independent voters. Throughout the race, Norton and Buck have battled for the conservative high ground.

Norton rolled out an endorsement from the founder of the Minuteman Project over the weekend. Last week, Norton won the backing of Arizona Gov. Jan Brewer (R).