PHOENIX » J.D. Hayworth is a large man, and to compensate for his indulgences, he hits the elliptical trainer every morning at 4, zipping along to an incongruous soundtrack of Elvis Costello, Frank Sinatra and old advertising jingles.

Until recently, he would then repair to a local radio station, where he would spend the better part of the day denouncing, in no particular order, illegal immigrants, all things Barack Obama, those who are insufficiently patriotic and, his favorite mark, one John McCain, the senior senator from Arizona.

Now, Hayworth, a former Republican congressman, is preparing to expand his political appetite for McCain by formally announcing on Monday what everyone in this state has known for months, his challenge to the senator in the Republican primary in August.

Hayworth hopes that by standing on the intersection of opportunity and timing, he can lure enough Tea Party sympathizers fresh off their convention in Nashville, Tenn., seducible independent voters (Arizona has an open primary) and conservative Republican grass-roots activists, who have long been disenchanted with McCain.

“;The political winds of change are here,”; Hayworth said over lunch. “;The conservatives are highly motivated and there is an intensity level among conservatives to take part in this primary. The atmospherics will help us.”;

Still bruised by his presidential run and struggling to find his footing in the fractured Republican Party, McCain remains a formidable force in his home state, through the sheer power of his name and fat campaign coffers. Most political analysts suggest Hayworth begins as the underdog, and McCain's supporters say they are confident.

“;Sen. McCain takes every race seriously,”; said Brian Rogers, a spokesman for the senator's re-election campaign, “;and is confident that the voters of Arizona will again return him to office as they have done in the past, and he is working hard to earn their continued support.”;

Yet McCain now finds himself jammed, moving starkly—and often awkwardly—to the right, apparently in an apparent to gain favor among the same voters whom Hayworth, a consistent voice for the far right, could pull toward him like taffy come summer.

McCain now sharply criticizes the bailout bill he voted for, pivoted from his earlier position that the Guantanamo Bay detention facility should be closed, offered only a muted response to the Supreme Court's decision undoing campaign finance laws and backed down from statements that gays in the military would be OK by him if the military brass were on board.

“;John is undergoing a campaign conversion,”; Hayworth said.

Hayworth's radio personality bluster and big emotions—he teared up in an interview when describing the film “;The Blind Side”;—were once the stuff of eye rolls, but may now have a part in the greater populist narrative that threatens many of the nation's more centrist Republicans.

McCain, a tireless campaigner since he was first elected to the Senate in 1986, is taking nothing for granted. He has clocked many hours doing town hall meetings and other campaign events and has already aired three radio advertisements in Phoenix.

His campaign, concerned that Hayworth was taking an unfair—and possibly illegal—advantage of his position as a talk show host on the right-leaning radio station KFYI (550 AM), filed a complaint against him with the FCC; Hayworth quickly resigned from his spot, bringing an end to such orations as “;get ready for earthquake amnesty”; after the earthquake in Haiti.

McCain has been long vexed by the more right-leaning corners of the Republican Party, especially the ones here at home, who are forever straw-polling their way toward his (fictional) downfall. His support for immigration policy overhaul, campaign finance restrictions and his past opposition to the Bush administration tax cuts and the Federal Marriage Amendment all contributed to his problems here.

In 2008, signs of McCain's weaknesses at home were revealed. He won 47.2 percent of the vote in the Republican presidential primary, a clear victory but hardly overwhelming for a hometown guy.

“;J.D. is our great hope,”; said Rob Haney, chairman of the Maricopa County Republican Party, home to Phoenix, and McCain. “;McCain has been a thorn in our sides for years. A dagger in our backs, really.”;McCain and Hayworth are not lifetime adversaries. During McCain's presidential run in 2000, Hayworth campaigned for him aggressively. But the two parted ideological ways shortly after that election, and Hayworth has been dinging him ever since.

But on balance, McCain has enjoyed a deep base among the state's more centrist Republicans, independents and Democrats, and his fundraising abilities—he has roughly $5 million in the bank for this race—and greater institutional support statewide have been unbeatable.

Even within the fractured Tea Party movement, McCain is not without support. He is endorsed by Sen. Scott Brown of Massachusetts, the populist movement's darling, and Sarah Palin, his running mate in the 2008 presidential campaign. And Dick Armey, whose FreedomWorks organization has become front and center in the movement, says he is throwing his support behind McCain.

Further, many Arizona Republicans are not eager to offer any hope in the general election to the Democrats, who so far have no challenger for the Senate seat but might become animated by the possibility of Hayworth to smack around.

Indeed Hayworth, a former sportscaster who rode the 1994 wave of conservatism into Congress, where he then served six terms, has political baggage. He was a very large recipient of both money and largess—like sports skyboxes—from the disgraced lobbyist Jack Abramoff. His loss to Democrat Harry Mitchell in his 2006 re-election bid was humiliating, and underscored voter distaste for some of his more boisterous ways.

In interviews with roughly 20 Republican voters in Scottsdale and the conservative city of Gilbert, not a Hayworth supporter could be found. “;I think McCain's doing a yeoman's job, and I'll vote for him as long as he runs,”; said Jerry Ebner, 59, a computer consultant in Scottsdale.

However, even at this early juncture, the Arizona primary is shaping up to be among the more high-profile Republican races nationally.

“;Arizona Republicans are more energized than they have been in recent memory,”; said Matt Roberts, a spokesman for the state's Republican Party. “;That energy between the two candidates will push turn out and I think it will be a pretty dynamic for both of them.”;

Ever eager to sprinkle beads of approbation for the storied man he hopes to bring down, Hayworth couched his confidence in compliments.

“;We all admire and respect John for his service,”; he said. “;But he's been there too long, and it's time to welcome him back home.”;