Vice presidential picks don’t matter. Except when they do. If John Kerry had chosen Dick -Gephardt instead of John Edwards in 2004, and had then parked Gephardt in Ohio during the general election campaign to make the Democratic case to working-class voters, Kerry might well have won the Buckeye State—and the presidency. In 1992, Bill Clinton’s selection of Al Gore, a Southerner and hawkish, confirmed the notion that Clinton was a different kind of Democrat, and the successful Clinton-Gore bus tour following the convention helped lock in their huge post-convention bounce that put the Democratic ticket ahead for good. In 1980, Ronald Reagan’s selection of George H. W. Bush helped unite the party, minimizing the damage the renegade liberal Republican John Anderson could do running as an independent in the general election. It also showed Reagan as a confident and strong leader, willing to pick his toughest opponent as his running mate.

Of course, Kerry might have lost anyway. And maybe Reagan and Clinton were fated to win. But maybe not.

And maybe Mitt Romney’s selection of Paul Ryan won’t end up making much difference. But we think it will. The selection has changed the nature of the 2012 presidential contest. It means we now have a big campaign, about big issues and big choices. During the summer months, the Romney campaign was fighting and losing a trench warfare battle. Now the Romney-Ryan ticket has a good chance to win a large-scale electoral war of maneuver.

Furthermore, Ryan will help in the Midwest—as Gephardt would have in 2004. The addition of a bold reforming conservative gives the GOP ticket a new character, even more than Clinton’s addition of Gore helped confirm a changed Democratic image in 1992. And the selection of Ryan is a strong, self-confident pick, reflecting well on Romney, as the pick of Bush in 1980 spoke well in a somewhat different way of Reagan.

But perhaps the most important effect of the Ryan pick is this: It turns the GOP effort from a campaign into a movement. It transforms a mere electoral effort into a political cause. The Romney 2012 campaign no longer brings to mind its Republican predecessor, the McCain campaign of 2008. Instead, Romney-Ryan could end up more closely resembling Obama 2008.

In 2008, Obama was the young forward-looking reformer, running on a big (if gauzy) message. He was able to capitalize on opposition to the Bush administration without seeming merely oppositional. He was able to enliven his campaign by his own presence and skills. Now it’s the Republicans who are running on a newly bold conservative message, presenting a hopeful choice for change rather than mere opposition to the status quo, and on a ticket enlivened by Ryan’s presence and skills.

Until last week, the Romney campaign was a few hundred operatives working hard in Boston trying to win a presidential election. Now Romney-Ryan is a groundswell of citizens spontaneously writing, volunteering, and proselytizing on behalf of a cause. The first was going to be a grueling uphill climb. The second could be more like running downhill with the wind at your back. Even in the second instance, of course, the candidate still has to jump the hurdles and avoid the obstacles. But it’s a lot easier to prevail when you stand for a cause citizens are eager to join than when you’re engaged in a campaign voters may diffidently support.

The best Republican electoral years in modern history were 1980, 1994, and 2010. Until last week, 2012 didn’t feel like any of them. Now it does. With the addition of Paul Ryan, we have a bold and forward-looking Republican ticket that seems to match the moment. Perhaps Romney knew all along that “he is prosperous who adapts his mode of proceeding to the qualities of the times.” Or did he spend time, while contemplating his vice presidential pick, surreptitiously studying the works of the wily Florentine?