Roughly two days after Republican presidential candidate Mitt Romney plucked Paul Ryan from near-total wonk obscurity — those who knew his name before this past weekend generally resided at think tanks in Washington — to be his running mate, he has now become a familiar face to anyone with even a passing interest in national politics.

So, what have we learned about Ryan — and Romney — since Saturday morning? Below are five observations on how the choice has reshaped the campaign:

1. Ryan has energized Republicans. Read any report out of the Ryan-Romney bus tour through Virginia (Saturday) and North Carolina (Sunday), and it’s clear that there is an energy in the crowds that wasn’t there a few days ago. The question is how long that positive buzz will last. Remember that then-Alaska Gov. Sarah Palin drew huge crowds during her first few days (and weeks) as Sen. John McCain’s running mate in 2008. And we know how that worked out. For the moment, the fresh face and Midwestern aw-shucks mentality that Ryan exudes seem to have Republicans excited about their presidential ticket anew — or for the first time.

2. Romney and Ryan have chemistry. Romney’s default mode is reserved — no matter the circumstances or the stakes. That’s why it has been striking to watch him interact with Ryan. After introducing the congressman as “the next president of the United States” in Norfolk on Saturday — Romney may be excited about Ryan, but he is still a bit gaffe-prone — he bounded onstage, slung his arm around Ryan’s shoulder and corrected himself. It was as close to natural as Romney gets. Then on Sunday in North Carolina, it was Romney joining in the “Paul” chants with the crowd. What these moments show is that Romney genuinely likes Ryan, a quality that shouldn’t be underestimated on a ticket.

3. Romney won’t run on the Ryan budget plan — and Democrats won’t let him get away with that. What Romney and his team seem to be hoping is that picking Ryan will send a symbolic signal to voters that the Republican ticket is serious about policy-making without having to be answerable for every jot and tittle of the controversial blueprint.

“Governor Romney’s vision for the country is something that Congressman Ryan supports,” Kevin Madden, a traveling spokesman for the campaign, said when asked about the Ryan budget. Democrats, smartly, refused Sunday to let Romney pull that bit of political sleight of hand. David Axelrod, one of President Obama’s senior advisers, repeatedly labeled Ryan a “right-wing ideologue” and sought to lay his budget at Romney’s feet.

4. Republicans think Ryan can reach independents. One of the most fascinating elements of the introductory speech that Romney gave for Ryan on Saturday was the emphasis on the Wisconsin Republican’s bipartisan credentials. “He doesn’t demonize his opponents,” Romney said at one point. “He understands honorable people can have honest differences.”

Then in a Sunday appearance on NBC’s “Meet the Press,” Wisconsin’s Republican Gov. Scott Walker touted Ryan’s “tremendous appeal to swing voters and independent voters.” That coordinated effort to portray Ryan as attractive to undecided voters in the center of the electorate — even as Democrats seek to paint him as a creature of the far right — is not accidental. There is some evidence that Ryan can win over voters outside the GOP base, as his congressional district has the potential to be competitive but never has been since he won it in 1998. But drawing across-the-aisle support in a non-targeted House race and doing it at the presidential level are very different things.

5. Putting Ryan on the ticket makes the choice in November even clearer. The differences between where Romney wants to take the country and where Obama has guided it over the past four years were already relatively clear to anyone even sort of paying attention. But, in choosing the face of the Republican vision for governance — deep changes to the social safety net, an emphasis on importance of the private sector — Romney is ensuring that the lines of demarcation between the Democratic and Republican tickets are as stark as they have been in modern memory. (Remember when people thought that the choice between George W. Bush and Al Gore was meaningless because they both basically believed the same things?) The addition of Ryan to the Republican ticket means that no one should go into the voting booth in 85 days wondering just what differentiates the two sides.