by Larry Sabato

The favored Republican adjective for Mitt Romney’s selection of Paul Ryan is “bold.”

The favored adjective for Democrats is “risky.”

The word that historians will choose to describe the selection, though, is anyone’s guess.

Ryan is certainly not the safe pick that a Rob Portman or Tim Pawlenty would have been. The House Budget Committee chairman is perhaps the leading conservative economic spokesman in the Republican Party, and his now famous (or infamous) budget plan, with its changes to how Medicare is delivered and its multitude of cuts to social programs, became a major lightning rod earlier this cycle.

By selecting Ryan, Romney has essentially taken ownership of Ryan’s budget ideas. That’s probably a relief to Republicans, who question Romney’s commitment to the cause, but it also provides openings to Democrats, as the Ryan budget could be a potent political weapon in the fall, and not just at the top of the ticket.

His selection has also heightened the differences between the two party’s tickets; Romney’s actual beliefs on issues might be difficult to nail down, but Ryan’s aren’t. This is a big choice election, at least when it comes to budget and taxation issues.

And, frankly, that’s the way it should be — the nation does undoubtedly have questions about the future of its entitlement programs and the size of the national debt. Anything that promotes discussion of those national choices, as opposed to a national fixation on gaffes and attack ads, is welcome.

In picking Ryan, Romney is, in a way, emulating the vice presidential decision made by the man who beat him for the 2008 GOP nomination — John McCain.

Ryan, like Sarah Palin, is a pick designed not necessarily to appeal to independents or Democrats, but rather to excite the party’s base. Palin’s selection did that for McCain, at least for a time, but her candidacy fizzled after a number of slip-ups, including her now-infamous interview with Katie Couric.

Presumably, Ryan won’t make the same sorts of mistakes that Palin made, and it’s helpful to him that he’s much more familiar with the national press, which regards him as an intellectual.

Also, McCain’s base strategy couldn’t succeed in a year when the Republican Party was so damaged, when the economy was collapsing and when Barack Obama was running a historic, exciting candidacy.

But a base strategy might work this year because a motivated GOP base, despite its weaknesses with minority voters, might be able to outnumber the Democratic base in this election, much like it did in 2004.

It does not appear that Romney has his base fully behind him. His poll numbers, especially lately, have not been strong.

At the moment, Romney is slightly underperforming John McCain’s performance from four years ago. McCain received 45.6 percent of the national vote and 45.4 percent in key swing states that include Colorado, Florida, Iowa, New Hampshire, Nevada, Ohio and Virginia. Romney is scoring just 43.4 percent nationally and 44.5 percent in the swing states, according to Saturday’s RealClearPolitics average of polls.

There are Republican-leaning voters who still must be brought into the fold, and Romney has two big chances to win them over — through the vice presidential selection, and through his upcoming convention in Tampa at the end of the month.

The Washington Examiner’s Byron York recently reported, “Romney aides believe strongly that this race will play out like the 1980 campaign, in which President Jimmy Carter led Ronald Reagan for much of the race until Reagan broke through just before the election.” If that is indeed the campaign’s thinking — and that strikes us as more than a little overoptimistic even given the gloomy economic numbers — then it would make sense to pick Ryan with an eye to post-January policymaking as opposed to pre-November politicking.

Democrats are gleeful about the selection; Jesse Ferguson, the national press secretary of the Democratic Congressional Campaign Committee, tweeted on Saturday morning: “Hmm. So this is what Xmas morning feels like?”

Democrats are trying to nationalize the race for the House by using the Ryan budget against Republican incumbents, nearly all of whom voted for it in April 2011. The Ryan budget was always going to be part of this campaign, but given that its architect is now on the national ticket, it will be harder for other Republicans to downplay that vote.

At 42, Ryan is tied for the sixth-youngest major party vice presidential nominee in American history; John Breckenridge, James Buchanan’s running mate in 1856, was the youngest at 35.

A polished striver whose father and grandfather both died of heart attacks in their 50s, Ryan may be motivated by his unfortunate family history to climb the political ladder quicker than most.

LARRY SABATO is director of Sabato’s Crystal Ball, a nonpartisan unit of the University of Virginia. He can be reached at sabato@virginia.edu.