US House Majority Leader US Rep. Eric Cantor, R-Virginia, speaks during the House Republican Leadership press conference at the House Republican Issues Conference in Cambridge, Maryland, January 30, 2014. (JIM WATSON/AFP/Getty Images)

In a lot of ways, Dave Brat is your typical tea party-style insurgent running in a Republican primary this year. He's an economics professor at a tiny college, a striped-tie, free market enthusiast who decries debt and immigration. He has the backing of the crankiest conservative bloggers and radio hosts, one of whom, Laura Ingraham, appeared with him at a rally this week.

But Brat isn't running to unseat some mush-ball moderate or no-name state legislator backed by the local chamber of commerce. No, Brat's opponent in next Tuesday's primary is Eric Cantor, the congressman from Virginia's 7th District and the second most powerful Republican in the House. Which highlights a question that's becoming more germane as this season of Republican disunion drags on:

Just how conservative do you have to be before these conservative activists will leave you alone?

I mean, if the needling Cantor isn't Barack Obama's least favorite Republican on the Hill, he's certainly vying for the title. It was Cantor, you may recall, who forcibly put the brakes on John Boehner when the speaker was edging close to a comprehensive budget deal with the White House in 2011, because he couldn't stomach $1 trillion-plus in new revenue. He distinguished himself, during those negotiations, as the one guy in the room who didn't want a deal and who couldn't be bothered to disguise his contempt for the president.

Until recently, anyway, Cantor was known around Washington as the tea party's guy in leadership, a bridge between the pragmatic old guard (who found him a tick more tolerable than the other young punks) and the new ideologues (who hoped he might rise up and supplant Boehner as speaker).

But let's not trifle with all this wearying reality. Instead, let's look on Dave Brat's website, which features a photo of Obama and Cantor sharing a heartfelt moment as they emerge from the House chamber together, like a couple of newlyweds in Utah. The site says Cantor "distorts the free market" and has "embraced big government."

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Brat expanded on this critique when we spoke on the phone a few days ago. He told me Cantor had thrown his weight behind comprehensive immigration reform, refused to defund the president's health care plan and backed down on reducing spending and debt. "In the past few years, Eric has shifted dramatically, and that's the only way to look at it," Brat told me.

Well, maybe not the only way. Yes, Cantor declared himself open to a reform in the immigration system that would offer a path to citizenship for children who have spent their lives here, but, true to form, he opposed the only bipartisan bill that had a chance of passing. He has led House Republicans in voting no fewer than six times to defund the health care law (good luck with that), not to mention a few dozen other votes to strip various provisions.

As for austerity, the Cantor-led Republican caucus overwhelmingly passed Wisconsin Rep. Paul Ryan's budget plan, which would save billions by converting huge pieces of the Great Society into block grants and vouchers. ("It solves all the world's problems, with the possible exception of who should run Kashmir," is how Grover Norquist, the conservative anti-tax crusader, described that plan to me.) It's true that Cantor was one of only 28 House Republicans who voted to lift the debt ceiling without conditions last February, but that was clearly a show of support for Boehner, not some sudden burst of statesmanship.

The fact is, if you wanted a more reliable predictor of conservative orthodoxy than Cantor, you'd need IBM's Watson team to build it.

But what's going on here doesn't have a lot to do with ideology. It's really all about disdain for the governing establishment, which activists like Brat see as a bunch of corporate bullies. It turns out that Brat ran for state delegate two years ago and blames Cantor and his "Henrico mafia" — that is, the Republican Party of Henrico County, the heart of the 7th District — for making sure he didn't win. What got Brat most animated when we talked was the way Cantor had tried to freeze him out at last month's state party convention by renting out all the conference rooms at the Hilton.

"He's been working in the state and across the nation to get rid of tea partyers and conservatives," Brat said. "He's caused the fracture in the party, not me. He's in bad, bad shape with the grassroots in his own district."

This last part seems true enough. No one seriously suspects Cantor, who refused an interview request, is going to lose the primary next Tuesday, but he got something of a shock at the convention when activists booed him during his speech and rejected his handpicked candidate for county chairman.

Cantor's aides insist the primary challenge is more of an annoyance than anything else, but that hasn't stopped them from producing a few million bucks worth of increasingly shrill TV spots and mailers. Cantor calls Brat a "liberal college professor" (clearly he's never met Noam Chomsky), and he's told seniors that Brat wants to take away their Social Security — a pretty cynical strategy coming from a guy who has had to answer the same charges from Democrats.

Leaving all that back-and-forth aside, though, the real question is what the tea party crowd — and in this I include the Ingrahams and Rush Limbaughs of the world — thinks it's really accomplishing in a race like this.

The theory behind running primary campaigns against incumbents, generally, is that they get you outsize influence, even if you lose the vast majority of them. Other incumbents look at whichever of their poor colleagues is having to spend every last dollar to stave off an embarrassing defeat at the hands of some activist armed with a Facebook page and a bullhorn, and they think: I'd better make these people happy, or they'll come after me next. That strategy has worked pretty well for the tea party so far.

But the strategy works only if incumbents think they have a reasonable chance of placating the pitchfork-wielding mob. If leading Republicans can say all the right things and make all the right votes and lay prostrate before the talk radio gods, and still they end up fending off primary challenges and getting booed out of their own conventions, then they might just start to wonder: What's the point of all this cowering in the corner, anyway? If you're going to get slammed no matter what you do, then why not, you know, actually try to govern?

If Eric Cantor isn't anti-government, anti-spending, anti-Obama enough to insulate himself from grass-roots rebellion, then you've got to ask yourself: Who is?