For Republicans, call Paul Ryan the schizophrenic choice.

Even as they celebrated Mitt Romney’s decision to select the House Budget chairman as his vice presidential running mate, they acknowledged it carries political risks for the GOP ticket in the November battle against President Barack Obama. Democrats are uniformly elated, believing that the Wisconsin lawmaker’s blueprint to overhaul Medicare could be a dagger to the heart of the Romney campaign — and a lifeboat for Obama, whose re-election is threatened by a potential wave of voter discontent.

Conversations with Republican professionals and Twitter exchanges with some of my “very” conservative followers since Saturday’s announcement reveal the GOP’s split personality over the Ryan pick.

In one breath, they glowingly discuss how putting the Ryan on the ticket has transformed the presidential race from petty to serious, a signal that a Romney administration might tackle the country’s fiscal challenges with a conservative vigor not seen since Ronald Reagan. In the next, they anguish that Obama might overcome the handicap of 8.3 percent unemployment and anemic economic growth by defining the race as a fight to protect the popular social safety net.

“I love Ryan on policy, and the fact that Romney made such a risky pick helps me convince (sic) that he might be a [conservative] POTUS,” one of my followers tweeted to me this morning. But in subsequent tweets, this individual, who supported Rick Santorum in the Republican primary and has said he was disinclined to vote for Romney in November, added this: “BUT, I think this was a bad choice. [Romney] didn’t have to take Ryan — an easy target. … With Ryan on the ticket, Obama will easily continue to distract voters from the economy and high unemployment, to Medicare.”

A Republican operative based in Washington, D.C., who also is a Romney donor, suggested he was heartened by the former Massachusetts governor’s decision to choose Ryan because it indicates he’s not running just to win, but also to make a difference. “If Romney loses because the Ryan budget is unfair, then why would you want to win?” this individual said, in reference to the Ryan budget plan passed by the House that includes a controversial Medicare overhaul that Democrats contend would gut the program and raise costs for seniors. Republicans argue the plan would put Medicare on a more sustainable path and would only affect future, not current, beneficiaries.

But to the extent that winning matters, if for no other reason than to put the brakes on Obama’s agenda, this self-described conservative-at-heart-but-realistic Romney donor expressed concern. His biggest worry is that while Ryan has proved effective at times at winning the debate over his budget proposals, he cannot be everywhere in a national presidential campaign. And even if he could be, he needs to adjust his sales pitch to meet the circumstances.

“The campaign needs a coordinated message machine,” this Romney supporter said. “Even if he is present, Ryan needs to come up with a time-efficient explanation. He will not get 15 minutes to respond every time.”

So, stipulating for a moment that Ryan carries as much political risk for Romney as Democrats and nervous Republicans claim, what might have sold the presumptive GOP presidential nominee on the 42-year-old policy wonk? According to a knowledgeable Republican source I spoke with Saturday, the two men hit it off personally — and so did their wives, Ann Romney and Janna Ryan.

As Ryan told me during an interview in late May, he had been chatting with Romney periodically throughout the contentious GOP primary to discuss policy matters, and he came away with the impression that the career business executive and former governor “not only really understood the issues and the complexity of the issues, that he really had the fortitude to take these things on.”

But it was during the GOP primary campaign in Wisconsin, which came just as Ryan delivered a timely and much-needed endorsement of Romney as the former governor attempted to hold off Santorum, that they cemented a relationship that would become the foundation for Romney’s decision to pass over a wealth of perhaps more seasoned (and some might say, safer) Republican talent in his search for a running mate.

When “Romney was out in Wisconsin for that primary, there was a very strong connection, and Ann and Janna really connected. Obviously Ryan had the policy and political credentials. But the family sign-off helped on both sides,” the knowledgeable Republican source said. “They just had a connection that you can’t fake and can’t create.”