A hoarse but jubilant Rick Santorum gave a rambling, somewhat disjointed speech celebrating his wins in Tennessee and Oklahoma. (Later in the evening he took the North Dakota caucus.) As of this writing, Ohio is too close call, but Mitt Romney strongholds are starting to come in. If they continue to go Romney’s way (as did the urban and suburban areas of Michigan) he is positioned to win the crown jewel of the night.

Rather than making his blue collar economic pitch, Santorum focused nearly entirely on health care, hoping for the umpteenth time to use Romneycare to trip up the front-runner. He railed against Romney for his “top-down” health-care plan — and for allegedly advocating for it at the national level. The speech was a bit too long and undisciplined, which is true of many of his remarks.

Santorum won enough votes tonight to go on in the race, but it’s getting more difficult to argue he can actually win the nomination. After all, he claims to be the blue-collar vote-getter of the Rust Belt, but took a beating in Michigan and now seems imperiled in Ohio. He may be relieved still to be standing, but if he can’t win in Michigan or Ohio is he more than a regional candidate, a sort of Mike Huckabee with super PAC money?

Moreover, in failing to qualify for 18 delegates in Ohio or get on the ballot in Virginia Santorum’s path to the nomination is becoming less viable each week as his organizational limits take their toll. Moreover, with Newt Gingrich’s win in Georgia, those two will continue to vie for and subdivide the social conservative base, leaving Romney to march state-by-state toward the nomination.

For Romney, wins in Virginia, Vermont, Massachusetts and, most likely, Ohio will bolster his claim and certainly increase the parade of GOP officials who will endorse him in hopes of wrapping up the nomination race. But it will not wipe his opponents off the map. He may not be “inevitable,” but he remains the prohibitive favorite.

A relaxed Romney stressed the delegate count in his victory speech, noting that he was positioned to win more states before the votes are all counted tonight. He tried to give the primary an air of nostalgia, looking back on his progress toward the nomination. His opponents may not be giving up, but he is trying his best to pivot toward the general election. He avoided mentioning them at all.

Romney’s speech emphasized the people he’s met along the campaign trail and the plight of the middle class under Obama. He declared, “To the millions of Americans who look around and can only see jobs they can’t get and bills they can’t pay, I have a message: You have not failed. This president has failed you. President Obama said he would create jobs. For 36 months, unemployment has been above 8 percent. He said he would cut the deficit in half. He’s doubled it. Today, our debts are too high and our opportunities are too few. And we’ve seen enough of this president over the last three years to know that we don’t need another five. This president is out of ideas. He’s running out of excuses. And, in 2012, he’ll be out of office.”

He brought in a new theme: the fear of a second Obama term. He told the crowd: “President Obama seems to believe he is unchecked by our Constitution. He is unresponsive to the will of our people; he operates by command instead of by consensus. In a second term, he would be unrestrained by the demands of reelection. And if there is one thing we can’t afford, it is four years of a Barack Obama with no one to answer to. These days, the president and his team keep telling us that things are getting better. 24 million Americans are still struggling for work and they are high-fiving each other in the West Wing. But, my friends, the truth is this: 8 percent unemployment is not the best America can do; it’s just the best this administration can do.”

The night is emblematic of the race as a whole. Romney, with superior organization and a focused message, is striding toward the nomination. Santorum is hanging on, but not doing much more than that. Santorum would like to think the difference between the two is simply money. But in fact, Santorum’s message has become ragged and his wins in two relatively rural states do not bode well for his ability to build a winning coalition.