Santorum.

When Santorum was gaining on Romney in his home state of Michigan, Romney's Super PAC turned on the money ad spigot and preserved a narrow victory. It was the same story in pivotal Ohio. Romney's super PAC ran 3,313 ads in the final 10 days as opposed to only 722 for the Santorum super PAC. Romney squeaked out victory by four-fifths of a percentage point.

It was fitting that super PACs should bring the campaign to an end. Santorum announced he was dropping out of the race two weeks before the primary in his home state of Pennsylvania, and right after Romney's super PAC announced that they were about to spend $2.9 million in negative TV ads.

In the end Romney's super PAC spent $40 million in unlimited contributions fromthe end of our trip, with nothing in front of us but a two-hour jaunt down the broad, brutish Beijing Badaling Expressway to the capital. Ms. Lei, my delicate translator, had announced her wish to get back to Beijing before her four-year-old boy went to bed, and we were running late. Mr. Zhang’s swashbuckling solution was a “shortcut”: Instead of fighting his way along the paved, but circuitous, road to the highway, he sped down a narrow dirt path that held the promise of providing a more direct route. Within minutes he was doubling back on himself, loudly grinding gears as he cut through dust-shrouded cornfields and drought-stricken cherry orchards while peasants leaped out of our way and into the foliage. By the time Mr. Zhang found the