Arizona Sen. John McCain is headed to Colorado this weekend to campaign for Republican Senate candidate Jane Norton.
A spokeswoman for Norton says McCain will be in Grand Junction and the Denver suburbs Sunday for fundraisers and public rallies for Norton. Colorado Republicans are choosing between Norton and Weld County prosecutor Ken Buck in a mostly mail-in primary election that finishes Aug. 10.
Norton co-chaired McCain's Colorado campaign during the senator's 2008 presidential campaign. Some tea party leaders in Colorado have criticized Norton for being too cozy with McCain, whom some Republicans consider too moderate.
McCain faces a primary challenge in his own state Aug. 24.
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