MICHAEL BARONE: Romney-Ryan ticket puts entitlement crisis at center of campaign.

Romney’s choice was not much of a surprise after he told NBC’s Chuck Todd on Thursday that he wanted someone with “a vision for the country, that adds something to the political discourse about the direction of the country. I mean I happen to believe that this is a defining election for America, that we’re going to be voting for what kind of America we’re going to have.”

This arguably describes some of the others mentioned as possible nominees, but it clearly fits Paul Ryan.

He doesn’t fit some of the standard criteria for vice president. He hasn’t won a statewide election, held an executive position or become well known nationally or even in much of Wisconsin.

But more than anyone else, more even (as impolite as it is to say) than the putative presidential nominee, Ryan has set the course for the Republican party for the past three years both on policy and in politics. From his post as Chairman of the House Budget Committee, he has made himself not just a plausible but a formidable national nominee by advancing and arguing for major changes in entitlement policy.

He has argued consistently that entitlement programs — Social Security, Medicare, Medicaid — are on an unsustainable trajectory. Left alone, they threaten to crowd out necessary government spending and throttle the private sector.

Few public policy experts, on the center-left as well as the right, disagree. But many politicians, certainly those in the Obama White House, shy away from confronting the entitlement crisis. Better to demagogue your way through one more election cycle and kick the can down the road.

That’s going to be harder to do, now. Plus this:

Ryan and Romney can make the point — lost in the shuffle when this is a low-visibility issue — that their plan leaves the current Medicare system in place for current recipients and those over 55. Those who have made plans based on the present program can continue to rely on it.

But they can also make the point that their reforms are necessary in order to make sure Medicare is sustainable in the long run. Polls show that many voters under 55 doubt that they’ll ever get the Medicare and Social Security benefits they’ve been promised.

One more thing about Ryan, I think, appealed to Romney. He has already shown he cannot be intimidated by the most eminent opponent. Watch the video of Ryan’s five-minute evisceration of Obamacare at the president’s Blair House meeting. You can tell that Obama didn’t like it one bit.

You know what will kill Medicare as we know it? Medicare as we know it. And he’s right about the intimidation bit. Compare to Tim Pawlenty’s failure at a crucial moment.

Also, Paul Ryan seems surprisingly popular among senior citizens. “Despite the attacks on Ryan over his budget plan, he’s easily the most liked of the short-listers among likely voters 65 years of age and over, with a 52/29 favorability rating. His ‘very favorable’ rating of 31% in the 65+ group is more than 10 points better than the other shortlisters in the Rasmussen survey (again, save Rice). Jindal did well, too, with a 44/28, as did Pawlenty with a 40/30 and Portman at 37/26, but Ryan’s draw among seniors outpaced all of them. Ryan has plenty of room to be defined in either direction with 35% of voters overall not having an opinion, but that’s only true of 20% of seniors — and Ryan already has a majority of them on his side.”

But then, a 2011 Gallup Poll showed that seniors liked Ryan’s budget plan better than Obama’s by a substantial margin.

UPDATE: Jennifer Rubin: 10 Ways Paul Ryan Annoys The Liberal Media. Only 10? Well, here’s one: “In choosing Ryan over less ideological figures Romney showed that he in fact cares about ideas, is determined to fix our fiscal problems and is devoted to free markets. Ryan in that sense validates Romney’s core beliefs.”

Meanwhile, the line to see Romney-Ryan this morning is over a half-mile long. More here.

ANOTHER UPDATE: Reader Carlos Myers writes:

For once, we have someone who will be competent to be President of the Senate. What does this have to do with Ryan and the VP pick? That is because the VP is also the President of the Senate. So main job of the VP isn’t to be a “heartbeat away from the Presidency,” but to lead the Senate. The office of the President of the Senate has been largely maligned through US history, and its duties have been largely cooped by the Senate Majority Leader. So the question is, would Paul Ryan be the man that will insist in taking leadership in the Senate or will he, like every VPs before him, just sit back in the shadows so as to not rock the boat?

I had some related thoughts on the legislative role of the vice presidency here, in the New York Times, and at somewhat greater length here, in the Northwestern University Law Review.

MORE: Social media pushback: Running scared: Obama frantically tweets ‘FACTS’ about Ryan; citizens respond with truth. “Oh, dear. President Obama’s Twitter feed is a hot mess of scared.”

STILL MORE: Romney-Ryan event packed — here’s a pic of the overflow crowd from Sister Toldjah.

Plus, GayPatriot tweets on the lack of counterprotesters: “There were a total of six Obama supporters on the mile road into the complex. It was sad.”