(CNN) -- The GOP's 2008 presidential nominee has earned a primary challenge from the right on Presidents Day.J.D. Hayworth, a former congressman from Arizona and radio host, is scheduled to announce formally Monday that's he's challenging Republican John McCain for his U.S. Senate seat.
Hayworth was to announce his candidacy at a news conference at his new campaign office in Phoenix. The event kicks off a scheduled three-day, 10-stop campaign swing through Arizona.
Hayworth, who served six terms in the House of Representatives before losing his 2006 re-election bid, stepped down last month as host of a conservative talk-radio program in Phoenix. He said he respects McCain's service but said the senator's been in Washington too long and isn't conservative enough.
"We all love and think the world of John and John's place in history is secure," the 51-year old Hayworth said Friday. "But John no longer represents the common sense conservative philosophy that most Arizonans share."