(CNN) - Rep. Jeff Flake is the heavy favorite heading into Tuesday's GOP Senate primary, which pits the six-term congressman against wealthy businessman Wil Cardon.
Despite being outraised by his opponent, Flake has seen strong backing from both establishment and tea party Republicans in his quest to win the open seat soon to be vacated by retiring Senate Minority Whip Jon Kyl.
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His challenger, however, has put up a tough fight. A political newcomer, Cardon has not previously held public office and runs his family's real estate investment firm, the Cardon Group. He's taken in a considerable amount of money this cycle–$9.6 million as of Aug. 8–but about 90% of his campaign war chest comes from his own pocket, according to reports from the Federal Election Commission.
Flake, meanwhile, has raised $5.4 million, without lending any money to his campaign. He also has the support of both Kyl and Arizona's senior senator, John McCain. Flake, known as a maverick, was a major backer of McCain early on in the senator's 2008 presidential bid.
The congressman also falls in the column of one of the few national politicians whom former Alaska Gov. Sarah Palin endorsed in a Senate race this cycle. While Cardon paints himself as the tea party favorite in the race, Palin backed Flake in July, saying the congressman has led a tough fight against "pork barrel spending."
"He's not afraid to 'go rogue' against his own party and its leadership," she wrote in her endorsement announcement.
The winner of Tuesday's race will likely go on to face former U.S. Surgeon General Richard Carmona, who did not undergo a competitive Democratic primary battle.