The aftermath of the government shutdown hasn’t done much to cool the tempers of Republicans angered by their humiliating defeat at the hands of President Obama. Rather than accept responsibility for the failure of the no-win strategy they steered their party into, Tea Partiers are venting their frustration at the so-called establishment and vowing to try to defeat all those who don’t meet their standards for conservative purity even if that means dooming any hopes for the GOP to retake the Senate. Front and center on the list of the Republicans on their hit list is, of course, Senator John McCain of Arizona. Which is why his announcement earlier this week that he is seriously considering running for a sixth term in the Senate isn’t so much an indication of his desire to hold his seat as it is his throwing down of a gauntlet to a faction of his party that he hasn’t hesitated to describe as “wacko birds.”

It’s not likely that there is a Democrat in the state that has much of a chance to beat McCain either in 2016 when he will be 80 or even six years after that should he wish to keep going. But despite his general popularity, it is an open question as to whether McCain can win another Republican primary. Which means that if he does want another term, Arizona looks to be ground zero in an all-out war between a man who has become the quintessential GOP moderate and Tea Partiers who regard him as the incarnation of everything they dislike about “moderates.”

It should be recalled that the last time he faced the voters, McCain had to tack considerably to the right in order to win another term. After long being identified as a supporter of immigration reform and a path to citizenship for illegal aliens, McCain sang a slightly different tune in 2010, memorably demanding that the government build a wall along the border with Mexico. The shift, combined with a weaker than expected challenge from former congressman and talk show host J.D. Hayworth, worked nicely and the veteran senator won his primary in a walk and coasted to victory in the general election. But it isn’t likely that he can play the same game again or that he would even want to.

After antagonizing right-wingers by being the leading Republican sponsor of the bipartisan immigration reform bill passed by the Senate (though it will die in the House), McCain’s open contempt for Rand Paul’s filibuster about drone attacks, and his even greater disdain for those like Ted Cruz and Mike Lee, who urged Republicans to threaten a government shutdown to de-fund ObamaCare, his relations with the Tea Party can best be described as open warfare.

With the core of the party tilting further to the right there are those who assume there’s no way that McCain could survive a primary. After having antagonized conservatives on issues like campaign finance reform for decades, the dispute over the shutdown may be the final straw. Should a credible conservative, or at least one more credible than the likes of Hayworth, emerge against him, McCain will be in for the political fight of his life. Given his penchant for reaching across the aisle and an internationalist attitude on foreign policy that seems out of touch with many on the right these days, McCain is now routinely described by even as normally sober a politician as Liz Cheney as a “liberal Republican.” Though the label is more than a bit unfair, it means he will have a hard time winning a primary in such a conservative state.

That said, those who are inclined to write McCain’s reelection off as a lost cause should understand that the rules have always been slightly different for McCain. As a bona fide legendary war hero, McCain’s career has always been based as much on biography as it has a willingness to stick to conservative positions. Five years of torture in the Hanoi Hilton during the Vietnam War earned McCain a lifetime get-out-of-jail-free card as far as many Republicans have been concerned.

It should also be said that branding McCain as “liberal” is a bit of a misnomer. On most issues of concern to conservatives, McCain is with the base of his party. Indeed, the desire of many on the right to exact revenge on him over the perception that he betrayed them on the shutdown is undermined by the fact that, as he said this week, he fought the adoption of the president’s health-care program tooth and nail before Cruz and Lee were even elected to the Senate.

Though there are issues on which he has disagreed with many Republicans, his image as a moderate is based as much on his negative views of Cruz and company and a desire to work with Democrats as much as possible. As such, no shift to the right on any issue such as immigration will win over his conservative critics the way it did in 2010. If he is to win another term, it will have to be by proving that a centrist, or what passes for one in the GOP these days, can still win a primary in a red state. That’s the sort of a challenge the always-combative McCain may relish. Indeed, given the fact that he has talked about retirement, a desire to smack down the Tea Partiers might be the only reason he is thinking about running again. But it flies in the face of everything we know about the changing face of the base of the Republican Party. While it is always a mistake to underestimate the Navy veteran turned Washington institution, the odds against him sitting in the Senate in 2017 are very long.