Mitt Romney's selection of Paul Ryan, the Wisconsin congressman and House Budget Committee chairman, as his vice-presidential running mate in August 2012 was unusual in that it generated something rarely seen in political announcements: genuine enthusiasm on both sides of the partisan divide.

Republicans were pleased, or at least the activist and ideological core of the party was pleased, because Ryan was exactly the kind of selection that energized the base. He was young, articulate, and identified above all with a budget proposal — the Ryan Budget — that embodied the fiscal conservatism many in the party had been demanding: significant reductions in domestic spending, changes to Medicare that critics called a voucher program and Ryan called "premium support," and tax cuts that Ryan argued would generate growth sufficient to offset revenue losses.

Democrats were pleased, or at least Democratic strategists were pleased, because Ryan's selection handed them a gift: a vice-presidential candidate who had put his name on a specific, detailed plan that could be picked apart, attacked, and used to frighten particular constituencies. The Medicare changes in particular gave Democrats a powerful line of attack with older voters, who had been a Republican demographic strength and who were now being asked to accept significant uncertainty about their future healthcare.

The independent center was more genuinely uncertain. Ryan represented a clear ideological direction, not a moderation of Romney's positioning.

The selection clarified the choice in the election but did not obviously broaden Romney's coalition. Democrats' ability to run against "the Ryan Budget" proved to be exactly as potent as they had hoped. The Obama-Biden ticket won reelection in November.