Two days before the contest ends, though, the former Colorado lieutenant governor launched a cross-state sweep promoting her association with McCain, whom she called an "American hero."
McCain told reporters in suburban Denver he came to the state two weeks before his own Republican primary because he wanted to urge Republicans here to choose Norton over Weld County prosecutor Ken Buck.
"We need a lot of help right now," McCain said, talking about Republicans in the Senate.
McCain denied urging Norton to enter the race. Conservatives in Colorado have griped that Norton, who co-chaired McCain's 2008 presidential campaign here, was hand-picked by party leaders and McCain for the nomination. McCain said he didn't urge Norton to run until she and her husband called and asked his advice.
"They asked for my advice, and I said, 'Absolutely.' But I'm sure that there were many others, both in Washington and in Colorado and surrounding states, that also made that same recommendation," McCain said.
McCain joined Norton for a closed-to-the-public fundraiser before flying to Grand Junction for a campaign rally at Mesa State College.
Norton told reporters Sunday she "won't always agree" with McCain, but she thanked him for supporting her.
As in previous campaign appearances, Norton described herself as tougher than Buck on Afghanistan, where she has called for armed forces to "double down" while Buck has questioned American strategy there.
Buck said Sunday the two aren't that different on the war.
"We both want victory for America in Afghanistan," he said. He dismissed the McCain events, saying they wouldn't help Norton.
"It's not surprising to me that McCain would come to support his hand-picked candidate," Buck said.