The National Rifle Association has endorsed John McCain in Arizona's Republican Senate primary.
The organization announced its endorsement in a letter to McCain dated Thursday.
The endorsement is a significant boost for McCain. It provides high-profile support for his conservative credentials as he tries to shake a primary challenge by former U.S. Rep. J.D. Hayworth.
Hayworth has attacked McCain's record on gun rights, saying the four-term Senator has supported restrictive legislation.
Hayworth touts an endorsement from Gun Owners of America, a smaller gun-rights lobbying group.
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