The race has quickly become one of the most-watched Senate contests in the country, in part because Hayworth has tried to define himself as a tea party candidate taking on the establishment.
"I think that I'm the candidate of a majority of tea partiers," Hayworth said. "In Arizona, I feel very comfortable with the level of support we've received from the tea party movement."
Hayworth has been traveling the tea party circuit, speaking at rallies and neighborhood meetings around the state and arguing that he's the best candidate to champion tea party values of smaller government, free markets and fiscal responsibility.
Hayworth, who hosted a conservative talk-radio program after losing his seat to Democrat Harry Mitchell in 2006, has motivated a corps of conservatives who have been frustrated with McCain's history of working with Democrats to pass legislation.
McCain worked with Sen. Russ Feingold, D-Wis., on campaign-finance reform and with the late Sen. Edward M. Kennedy of Massachusetts on a bill that would have created a pathway to citizenship for illegal immigrants.
"McCain's served us well for 28 years, but government continues to grow," said Prescott Tea Party leader Michael Patrick Hendricks.
At a tea party meeting in Mesa last month, supporter Linda Pennis wore a button depicting McCain as a rhinoceros with a horn in place of his nose under the caption "RINO Hunters."