WASHINGTON – When Arizona’s bitter Republican primary election arrives in August, it is likely to be 102 degrees in the shade, of which there is little. It is the kind of weather in which only the hearty and highly motivated venture outdoors – Gila monsters and tea party activists. Which may not be good news for Sen. John McCain, who is generally disliked by the latter.

A recent poll puts McCain just five points ahead of J.D. Hayworth, a former congressman and radio talk show host who aspires to be Arizona’s Samuel Adams. McCain operatives dispute that the race is this close, but they cannot dispute that McCain is running in a political environment in which absolutely anything could happen to an incumbent.

The tea party movement resists both organization and generalization. But the outcome of Arizona’s Republican primary will do much to define it. The movement is often called “organic.” Both tulips and poison ivy are organic. And Hayworth is a toxic influence.

Hayworth’s 12 years representing parts of the Phoenix suburbs have been described by his former colleague Dick Armey as a “fairly short, undistinguished congressional career.” But Hayworth attracted national attention after an epiphany of sorts in 2005. Though he had previously sponsored legislation to create a guest worker program, Hayworth became a militant foe of Mexican immigration. Not just illegal immigration. Hayworth proposed a moratorium on legal immigration from Mexico. He declared an intention not merely to secure the border but to “stand up for our culture” – which implies that Mexicans adulterate American culture. Hayworth warned of activists who would create an Aztec state on the ruins of American sovereignty in the Southwest. He voted against an anti-immigrant measure – which, among other provisions, prohibited religious charities from aiding illegal immigrants – because he thought the legislation was too soft.

From 2004 to 2006, Hayworth’s share of the vote in some Hispanic-influenced precincts dropped by more than 20 points, and he was carried away in the national anti-Republican deluge. Hayworth now presses his anti-immigration message in a primary challenge to McCain – contesting for the right to run for the Senate in a state that is about 18 percent Hispanic. To this appeal, Hayworth has added a “birther” message accusing President Obama of “identity theft.” Here he is on legalizing gay marriage: “I guess that would mean if you really had affection for your horse, I guess you could marry your horse.”

Tea party leaders have been understandably reluctant to endorse a candidate likely to embarrass any movement elastic enough to include Hayworth. Both Rep. Michelle Bachmann and Sen. Jim DeMint have declared themselves officially neutral in the Arizona Republican primary. Sarah Palin has campaigned for McCain.

This skepticism is compounded by Hayworth’s congressional record, which puts him in a select group among would-be tea party heroes. He is, I would bet, the only tea party candidate with a history of hosting fundraisers in lobbyist Jack Abramoff’s sports skyboxes. How many other tea party revolutionaries have also been enthusiastic legislative earmarkers, or voted for the Medicare prescription drug benefit, or supported the 2005 highway bill, which included the “bridge to nowhere”?

There are reasons that McCain is politically endangered. He is the Senate’s most gifted practitioner of sudden, disproportionate anger. He often seems overly impressed by his own virtue. Many in Washington and Arizona would pay good money to see him humbled. His epic service is matched by epic flaws – but an insufficient commitment to fiscal conservatism is not among them.

A primary loss might be good for McCain’s soul. But it would be bad for his party and for the country. At his best, McCain is precisely what a senator should be – independent, passionate, unawed by power, unmoved by influence. He has quickened national debates on torture, the environment, immigration, military strategy in Iraq and Afghanistan, and the budget process. He now stands accused of sidling to the right during a Republican primary – of which he is guilty. But events of the last year have moved Republicans of every variety to the right, in reaction to the vast Obama overreach.

In contrast, Hayworth symbolizes the worst excesses of the tea party movement, without having displayed any of its redeeming fiscal virtues while in office. His candidacy presents a test. If the movement embraces politicians such as Hayworth, it will not only prove itself extreme; it will prove itself gullible.

© 2010, Washington Post Writers Group