He’s already given political culture one of the great euphemisms ever for having an affair. And now the Appalachian trail walker, Mark Sanford, has become a terrific example of one of the core ideas of political parties and democracy: It’s all about the primaries.

Sanford won back his old House seat in a special election on Tuesday. Smart liberal commentators noted that Republicans had little choice. Paul Krugman:

Carmen Reinhart and Kenneth Rogoff wrote a wildly influential book four years ago called This Time Is Different.* The thesis of the book is that when a government has a debt-to-GDP ratio above 90 percent, it is terrible for economic growth. The authors also followed up with a couple of papers arguing the same thing. Pro-austerity forces here and elsewhere in the world have seized upon the book to push their favored policies.

This week, ten years after swearing to destroy Saddam Hussein and build democracy in Iraq, the United States took a step toward dismantling its investment in studying how democracy works. For more than 15 years, congressional Republicans have been trying to do away with federal funding for political-science research. Every time until now, political scientists successfully fought back. One reason they could: The pot designated for political science in the National Science Foundation was a tiny percentage of overall research money—about $10 million out of a $7 billion budget. That's less than two-tenths of a percent. But it's also the majority of total grant funding for political-science research. The field provides us with much of what we know about how democracies, including our own, function (and don't function). Political scientists study how and why opinions change on key issues, what motivates people to vote, and how public opinion influences elected officials. For a relatively small sum, the nation that loves to tout its democratic ideals has been funding projects to investigate how that democracy works (and doesn't).

For an ambitious politician, a spot on your party's presidential ticket is fraught with danger. On one hand, you immediately become a national figure, and if you win, you're vice president and you've got a good chance to become president. On the other hand, if you lose, you may wind up the target of contempt from forces within your own party and quickly fade away. Look at the list of recent VP losers: Sarah Palin, John Edwards, Joe Lieberman, Jack Kemp. None of them had any political future after their loss.

And then there's Paul Ryan. You have to give him credit for one thing. Unlike, say, Palin, he didn't let his time on the national stage give him delusions of grandeur. Instead of proclaiming himself the leader of a movement, he went right back to what he was doing before: using the budgeting process to push an extraordinarily radical agenda, all couched in enough numbers and figures to convince naive reporters that he's a Very Serious Fellow, despite the fact that his numbers and figures are about as serious as an episode of The Benny Hill Show. But this act is what got him where he is, and he seems to have concluded, probably wisely, that his best move is to get back on that same track, which might eventually lead him to the White House.