Note to Kevin McCarthy: The speaker of the House can do the job. Or he can keep it.

House Majority Leader Kevin McCarthy, left, with outgoing Speaker John Boehner on Sept. 29. (Photo: Jonathan Ernst/Reuters)

Anyone who has ever met both men can tell you that John Boehner and Kevin McCarthy are different kinds of personalities.

Boehner comes off like your high school girlfriend’s dad — reticent and intimidating when he opens the door and crushes your hand in his, wearing a golf shirt and khakis and holding a drink, although you know he’s going to break down as soon as his little girl leaves for the prom.

McCarthy’s more like your instant best friend, the guy with the half-cheesy smile who’ll kick his feet up on any coffee table. If he owned the local deli (which he did back in Bakersfield, Calif., once upon a time), you’d stop in just for the banter.

But anyone who assumes that being extroverted will make McCarthy more successful as a governing speaker of the House — a job he seems to have well in hand, now that Boehner has abruptly decided to quit Congress — should temper his expectations. The problem for Boehner had little to do, really, with his Midwestern reserve, or even his pragmatic philosophy.

It was more about the changed nature of the job itself.

There’s a reason the country saw fit to make the House speaker third in line to the presidency, behind the vice president and ahead of the Cabinet. (Yes, Kevin McCarthy is poised to become third in line to the presidency. Get used to it.)

Theoretically, at least, the speaker’s primary job is to forge some consensus in the House and to advocate that agenda in negotiations with the president. The speaker is the elected leader of the legislative branch, which, if you haven’t heard, is supposed to be an equal partner to the executive, as opposed to a nettlesome subordinate. He or she is, quite literally, speaking for the House.

That’s pretty close to the role speakers traditionally filled, right up until a few years ago. Contrary to popular myth, Tip O’Neill didn’t roll over for the Reagan agenda because he and the president shared a few drinks and some Irish folktales (although that probably helped). He negotiated the best deal he could, both for the country and for his own party’s majority, and then enacted it into law, because, you know, that’s sort of why Congress exists.

Newt Gingrich did the same thing when he reached accords with Bill Clinton, after much wrangling and brinkmanship, on welfare reform and a balanced budget. It’s worth noting that Gingrich’s speakership became untenable not because he made some concessions on policy to the White House, but because he lost seats in the wake of Clinton’s impeachment.

But here’s a news flash: Things have changed since 1998. The politics of both parties has become almost entirely oppositional. Nobody running for the House or Senate tries persuading the voters of anything affirmative anymore; it’s all about stopping the other party from ruining America, which is going to happen any minute now if we don’t all contribute five bucks in the next seven seconds.

Our last three presidents have started out with control of Congress only to see both houses change hands in off-year elections — a rolling wave of revolts that has never happened before in American history. And that means the speakership, for however long you can hold it, is most often now the pinnacle of resistance in government, rather than the instrument of congressional will.

Congress, we are forever being told, is the only thing standing between the country and some president’s ruinous, radical agenda. The speaker’s job is to obstruct and undermine, not negotiate or legislate.

And even in those rare moments when the president’s party controls Congress, the majority caucus expects its speaker to act as an ideological enforcer, making sure the White House imposes the will of the party, rather than caving to the forces of conciliation.

A successful speaker now has to relish his or her role as an ideological purist. The model here might be Nancy Pelosi, who seemed to flourish in the job and managed to run her caucus with admirable precision.

Pelosi effectively demobilized the soggy centrists in her own caucus, moving to install doctrinaire liberals in positions of power where she could. (This isn’t really an issue anymore, since most of the more moderate Democrats were then driven from office.) And because she enjoyed the confidence of her most ideological members, she was able to stifle rebellions when President Obama didn’t go far enough for liberals on health care or taxes.

This was never Boehner’s thing. An old-school believer in the institution as it was when he got there almost 25 years ago, Boehner, despite being unimpeachably conservative, had this crazy idea of himself as an actual speaker, someone who could negotiate big and lasting compromises like his predecessors. He had what you might call delusions of governing.

Which would have worked out great, if he had also had the designs for a time machine that could have taken him back to the days of Nirvana and Must See TV.

As it was, Boehner found himself trapped between the sizable minority of his caucus, outsiders who had ridden the wave into Washington and were determined to dismantle the place, and a partisan White House that wasn’t eager to inflame tensions with its own congressional allies.

The most consequential day in Boehner’s speakership may well have been the one in 2011 when, on the precipice of a historic budget deal, Obama suddenly demanded from him another $400 billion in tax increases to mollify congressional Democrats, and Boehner’s second-in-command, Eric Cantor, refused to even discuss a compromise. On some level, Boehner must have known then that he was a man out of time, relegated to the job of a resistance leader when all he craved was the chance to be a statesman.

McCarthy probably has easier relationships with a lot of the newer and younger members in his caucus. As a former whip, which is a job Boehner never held, he’s also bound to have a better sense of what each member needs in order to secure a vote.

But for a speaker to really legislate any meaningful compromise now, given how the job has evolved, he has to be something more like Nixon going to China, to use the old Washington cliché. The only kind of Republican speaker who could actually persuade his caucus to govern these days is probably one who generally shares its distaste for governing.

That’s not McCarthy. He seems like a guy who likes to get you to “yes,” rather than to always say “no.” Near as I can tell, Bakersfield Republicans aren’t the kind who stock concrete bunkers with purified water so they can ride out the inevitable collapse of the welfare state.

It seems increasingly likely that, to keep order in the caucus, McCarthy, like Boehner and Denny Hastert before him, will end up relying on a more strident majority leader who has the loyalty of his more nihilistic members — someone who ultimately wants the speakership for himself. Like Boehner, McCarthy will at some point have to choose between doing the job and keeping it.

At least until the next tsunami of revolt washes him and his party away.