(CNN) -- John McCain will continue the fight to retain his Senate seat Friday as he debates his competitors in Arizona.
McCain will square off against former Rep. J.D. Hayworth and Tea Party activist Jim Deakin in a debate at 7 p.m (10 p.m. ET) at the studio of CNN-affiliate KTVK in Phoenix.
The three are vying for the Republican nomination for the U.S. Senate seat. The primary is scheduled for August 24.
McCain is widely ahead of his two challengers, according to a poll released this week.
A Behavior Research Center survey indicates that 64 percent of likely Arizona Republican primary voters support McCain, and 19 percent Hayworth. Five percent support Deakin and 12 percent are undecided.
McCain, the GOP's 2008 presidential nominee, is bidding for a fifth term in the Senate.
The poll was conducted between June 30 and July 11, after media reports that Hayworth appeared in a 2007 infomercial that promised billions of dollars in free government grants. The McCain campaign subsequently launched two television ads that targeted Hayworth's past ties to the company that aired the infomercials.
The company -- National Grants Conferences -- has been criticized by the attorneys general of multiple states for deceptive marketing and has an "F" rating from the Southeast Florida and Caribbean Better Business Bureau.
McCain led Hayworth 54 percent to 28 percent in their previous poll, conducted in April.
Earl de Berge, the center's research director, says that McCain has hurt Hayworth "on ethics issues pertaining to being a lobbyist and so on. Most Republicans just pinch their nose at that stuff, and I think it just turned them off to him. It's the devil you know versus the devil you don't now."