Can Romney define himself amid Ryan differences?

"Defining moment" is an overused phrase in politics, but not this week. Mitt Romney’s selection of Paul Ryan as his vice presidential running mate has all the appearances of making these weeks another potential pivot point in the 2012 campaign.

Romney is enjoying an initial burst of energy from adding Ryan to the ticket. He is drawing the biggest and most enthusiastic crowds of his campaign, in the same way that GOP presidential nominee John McCain did four years ago after naming Sarah Palin as his running mate. He is getting what he hoped when he passed over safer and less exciting candidates.

But he has also bought some trouble. Romney appears to be struggling to carve out an identity that takes the best of what Ryan offers while insulating himself from the most controversial elements of Ryan’s budget blueprint. That has put the presumptive Republican nominee on defense again at a moment when he needs to be on offense. He can’t afford to stay in that posture very long.

Romney and his advisers insist that he will be running on his plan, not Ryan’s. In part, they’ve done that to remind people that the tail will not wag the dog, that the running mate will not overshadow the nominee. All presidential nominees would say the same thing. Where there are differences between a presidential and vice presidential candidate - as there always are - the running mate defers.

That should go without saying, but it’s far easier to make that argument when the running mate isn’t known as the intellectual leader of the party, or certainly of House Republicans, and when the running mate hasn’t been in the thick of the battle over how to transform government through tax cuts, budget cuts and entitlement reform.

Romney has embraced the conceptual framework of Ryan’s blueprint. He did that long before he selected Ryan as his running mate. But at the time he did that, he preserved some space to say he wouldn’t follow Ryan’s outline in all its details.

Now he’s in a different place because Ryan will be on the ticket. What Romney hasn’t said is whether he has real differences with Ryan or whether those differences are so minor as to make their plans indistinguishable. If there are substantive differences, they ought to be highlighted and explained. Are his advisers truly distancing themselves from some important policy ideas that Ryan has proposed? If not, that needs to be made clear.

In truth, on the big issues, Romney and Ryan are in agreement. They favor big tax cuts in which the wealthiest Americans would benefit. They back cuts in domestic discretionary spending. Both support changes that would convert Medicare into a premium support program for younger workers. Romney wants significant reforms in Social Security as well. Their priorities are the same.

Romney hoped that the choice of Ryan would amplify his message that the status quo or even small changes aren’t going to solve the country’s fiscal problems. That is a big argument and a debate worth having. But Romney hasn’t yet found a way to elevate the campaign debate effectively. Instead he’s dealing with questions about whether this or that aspect of Ryan’s plan is onerous or damaging to seniors or the middle class or the poor.

In short, Romney has given the Democrats a new opening to attack. President Obama is traveling across Iowa doing everything he can to tie the Republican ticket to congressional Republicans, whose favorable rating is in the basement. Vice President Biden is attacking Ryan, almost as if he is the nominee.

Obama campaign advisers are brushing aside any idea that there is daylight between Romney and Ryan and focusing on Ryan’s budget for what is likely to be a heavy campaign of negative ads. The Democrats are using August as they used July, to define the opposition negatively before Romney - and now Ryan - fully defend and define themselves.

Romney’s campaign has opportunities. Obama’s economic record remains a major problem and the biggest threat to his reelection. Obama is vulnerable as well to the criticism that he is not offering real leadership on entitlement reform.

Obama’s campaign would say that he was prepared to make a grand bargain last summer with House Speaker John A. Boehner (R-Ohio) and that the speaker backed away. Republicans have a different view of what scuttled those talks. In any case, those backroom negotiations aren’t the same as the president laying out a concrete agenda in this campaign that would show his real priorities there.

Romney eventually may get to all this in a more effective way. His convention may be that moment when the campaign ties it all together - the candidate’s biography presented in its most positive way; the policy differences with Obama outlined with clarity; the economic and fiscal arguments advanced with sharpness and elevation. The campaign may look and feel different at that point.

But Romney and Ryan face the possibility that, before the Tampa convention, Obama and the Democrats will define Ryan’s budget - and in particular his changes to Medicare - so negatively that the damage will be long lasting. For now, the most effective offense by Romney may be a more vigorous defense. That’s what makes these weeks a defining moment.