NBC News reports, "with a high degree of confidence," that Mitt Romney is down to three candidates for his running mate: Sen. Rob Portman (R-Ohio), former Gov. Tim Pawlenty (R-Minn.), and Rep. Paul Ryan (R-Wis.). Of the three, Ryan, formerly considered a long shot, is easily generating the most passionate responses. Republicans are deeply split, say Jonathan Martin, Jake Sherman, and Maggie Haberman at Politico, with the "cautious," pragmatic camp arguing that the House budget wonk is too risky a choice, and the "go bold" crowd insisting that Ryan would reinvigorate the "boring white guy" Romney campaign, give it some needed conservative policy heft, and maybe even tip Wisconsin into the GOP side of the electoral ledger. A look at why Romney shouldn't pick Romney as his running mate:

1. Two words: Ryan budget

The House GOP budget chief's signature achievement, a controversial government-slashing budget blueprint, is the top reason "Democrats are salivating — not literally but damn close — over the prospect of Romney putting Ryan on the ticket," says Chris Cillizza at The Washington Post. Ryan's big proposals to revamp Medicare, Medicaid, and Social Security are what endear him to conservatives, says David Graham at The Atlantic, but they also make him "an easy target for the other side, since voters tend to be horrified by deep cuts to entitlements and anything else that entails serious upward redistribution of wealth."

2. Choosing Ryan would make people worry about Medicare

With Ryan on Romney's ticket, the election would almost certainly become "a referendum over protecting the social safety net," not President Obama's economic record, says Josh Kraushaar at National Journal. That could doom Romney with the bulk of undecided voters, who are "inclined to vote Obama out of office" but rely on government entitlements. "A Romney-Ryan ticket could worry them enough that they'd vote for the devil they know." That's doubly true of Medicare recipients, says The Washington Post's Cillizza. Older voters are "the most reliable group of voters in every election — and a critical constituency for Republicans." Romney can't afford to lose them over "a budget plan he had no hand in crafting."

3. He's a creature of Washington, and Congress

One of Romney's great assets is that, with the federal government deeply unpopular, he doesn't have many connections to Washington. That distance from Capitol Hill changes with Ryan on the ticket, say Politico's Martin, Sherman, and Haberman. Ryan has spent seven terms in the House, and was deep in the weeds of Washington policymaking even before that, so Romney's having him as running mate would allow Obama to credibly "carve in the challenger a scarlet 'C' for the unpopular Congress."

4. Ryan is an untested campaigner

"One of the most curious — and little known — facts about Ryan is that he is not a terribly political creature," says The Washington Post's Cillizza. His focus on policy is admirable for a member of Congress, but "a lack of interest/acumen for the political game isn't a good thing in a vice presidential nominee." If you need an example of "picking a veep with little natural political instinct," think Sarah Palin. Ryan's never run outside of his safe congressional district, says The Atlantic's Graham. So "while he might be a very effective nationwide campaigner, he's simply not proven." That's a big gamble for risk-averse Romney to swallow.

5. And he's in a good spot where he is

"Perhaps a more important question than whether Romney would want Ryan is whether Ryan would have any interest in the job," says The Atlantic's Graham. At 42, he's already fought his way up to being "the undisputed GOP budget king," and jumping to an "impotent job" with the vice presidency could derail his bright future. Ryan's "young enough that he'll still have plenty of shots at the White House, Cabinet, or Senate if he wants them, whereas it's unclear where he'd go after four or eight years as VP."

Read more political coverage at The Week's 2012 Election Center.