Last night saw the release of three national polls — the first since Mitt Romney stepped into an all-consuming controversy over Bain Capital, outsourcing, and his tax returns. The first, from the New York Times and CBS News, shows Romney with a slight 47-46 lead over Barack Obama. percent. A bipartisan poll conducted for NPR shows Obama with a lead of two points over Romney (47-45), and another poll conducted for Fox News shows Obama with a four point lead over Romney (45-41).

Immediately, pundits took this as evidence that Romney had successfully weathered the attacks on Bain. But this strikes me as a little premature. Given the extent to which commentators have analogized this controversy to the Swift Boat attacks on John Kerry, it’s worth looking back at how the former nominee fared during the period in which he absorbed withering attacks on his military record. The Swift Boat ads aired from the beginning of May until the end of August. During this period, according to Gallup, Kerry held a small lead among likely voters.

Kerry’s position began to decline in August, but even then, he ended the month with only a small deficit. George W. Bush didn’t begin to build a large lead until the fall. The growth in Bush’s lead corresponded with a decline in Kerry’s net favorability. It’s possible Kerry was unaffected by the Swift Boat attacks. But it’s also possible that they didn’t begin to have an impact until later. It’s also too early to say whether the attacks on Bain will work. But there’s a chance they’ll have the most effect after the conventions, as undecided voters begin to make a choice, and draw on overall impressions built up over months as they make their decision. Given the new $8 million ad buy from Crossroads — meant to deflect Obama’s attacks on Bain — it’s clear Republicans see long-term danger here.

There’s also a second layer to the Bain attacks that is not even apparent yet: the policy dimension to the strategy. The attacks are also about creating an impression of Romney that will make it easier to get voters to believe that he really would cut Medicare and government programs that assist poor and middle class Americans while also cutting taxes for the rich. See Greg’s interview with Geoff Garin, pollster for Priorities USA:

“[O]nce people have learned that Romney was willing to fire workers and terminate health and pension benefits while taking tens of millions out of companies, they are much more ready to understand that Romney would indeed cut Social Security and Medicare to give tax breaks to rich people like himself. This provides a foundation to build the core policy critique against Romney.”

Democrats have yet to roll out the full spectrum of Bain attacks, and voters are still forming impressions of Romney. It’s only after this process runs its course into the fall — and only when undecided voters actually begin to decide — that we’ll see if they’ve been effective.

Jamelle Bouie is a Writing Fellow at The American Prospect. You can find his blog here.