The same way Ted Kennedy and John McCain did.
And it’s already showing results for Obama. Mitt Romney’s negatives are rising because of some initial attacks by the Obama campaign apparatus on Romney’s “core” and his Wall Street connections:
The Purple Poll, a survey of 12 swing states produced by the consulting firm Purple Strategies, spots some slight bleeding for Mitt Romney over the last two months of GOP primary season. It’s not that he’s making himself unacceptable to a general election audience, but Romney’s unfavorability rating has crept noticeably in the direction of the 50-percent mark …. The Obama campaign and the DNC are already grinding away at Romney with a negative message, and the former Massachusetts governor’s favorability numbers are headed in the direction Democrats want.
Romney does not have negatives as high as some other candidates, but that can change very quickly, as history shows. There is a reason David Axelrod and others on Team Obama have honed in on these themes. They have worked before.
You can pretty much disregard current polling showing Romney the most competitive with Obama. Romney has not survived these lines of attack in the past, so we should be suspicious that he can do so this time around.
If Romney is the nominee, expect these themes to be hammered relentlessly. And expect his negatives to be as high as any other Republican contender.