Sen. John McCain (R-Ariz.) is taking time away from his own campaign to help an ally in Colorado, perhaps the clearest sign yet the Arizona Senate primary may be all but over.

McCain will join former Lt. Gov. Jane Norton (R) on Sunday for stops in Denver and Grand Junction, Colo. The senator's appearance for Norton, according to her campaign, "will highlight fundamental differences between her and Ken Buck regarding the war on terrorism, especially the central front of the fight in Afghanistan."

Norton has sought to burnish her foreign policy credentials as she began trailing Buck in the polls. "Ken Buck's fundamental misunderstanding of the fight against terrorism is both reckless and dangerous. Terrorists aren't taught the tools of 'cost-benefit analysis' at terror training camps; terrorists are taught to kill American citizens," she said in a statement Tuesday.

One of the undercurrents in the Colorado Senate primary is the rivalry between McCain and Sen. Jim DeMint (R-S.C.), who has endorsed Buck. DeMint stumped for the Weld County district attorney last month.