On the first night of the Republican convention, Ann Romney tried to make Americans like Mitt Romney. Then Chris Christie took the stage and reminded them that, ideologically, this campaign isn’t about Mitt Romney. It’s about Paul Ryan.

Imagine that Romney had chosen Rob Portman or Marco Rubio or Tim Pawlenty as his running mate. Christie could never have given the tough-choices, eat-your-broccoli, let’s-be-respected-not-loved speech he gave Tuesday night. He could never have given that speech because until Romney chose Ryan, that wasn’t the message of the Romney campaign. After all, when you think about politicians noted for telling people hard truths they don’t want to hear, Romney isn’t the first guy who comes to mind.

Ryan has changed all that. He’s filled the ideological vacuum left by Romney’s own lack of ideological conviction, and now the rest of the party is following suit. I can’t think of a prior vice-presidential pick who has transformed the character of a campaign remotely as much.

The problem is twofold. First, the Ryan-Christie sacrifice argument assumes that America’s biggest problem is its debt. Putting aside the GOP’s dubious credentials as debt fighters, most Americans disagree. They think lack of jobs is America’s biggest problem. Until they chose Ryan, the Romney campaign understood that. Now they’re trying to act as if slashing the deficit and creating jobs are the same thing, which is neither true, at least in the short term, nor what most Americans believe.

Second, it’s not clear that Romney, who desperately needs Americans to find him more authentic, can achieve that with Ryan’s message. Christie’s speech was compelling because he’s a confrontational guy who seems to like picking fights with people by telling them what he considers to be hard truths. In a different way, sacrifice is an authentic message for Ryan as well. But it’s not an obviously authentic message for Romney, which is why Christie’s speech felt more like an advertisement for himself than for his party’s nominee. Sacrifice wasn’t the message of Romney’s governorship, his 2008 presidential campaign, or his 2012 primary campaign. Conservative Republicans love the message, but it’s not a message well designed enough to bring out the real Romney, if there is such a person, because it’s not the message that flows naturally from Romney’s own experience in politics and life.

It reminds me a bit of Bob Dole, another fairly nonideological candidate with an awkward relationship to his party’s base who chose a right-wing ideologue, Jack Kemp, as his running mate and tried to run a campaign of tax cutting when his heart wasn’t really in it. To be sure, Romney is more disciplined, articulate, and energetic than Dole, and the country’s conditions favor him far more. But Americans have a way of telling when candidates aren’t leveling with them about who they really are. As Labor Day approaches, Romney has found a message. Ryan gave it to him. Christie articulated it well. But I’m not sure it’s a message that will make people connect to Romney. In that sense, what Ann Romney tried to achieve in the first nationally televised speech of Tuesday night, Chris Christie may have undone in the second.