What happens when an incumbent running for re-election has a signature achievement in his first term that voters strongly dislike?  Barack Obama has that problem with ObamaCare among swing-state voters, and finds himself behind both of the leading Republicans in the new USA Today poll of these states:

Though the law has avid supporters, especially in the president’s Democratic base, the net effect among middle-of-the-road voters is negative for him. What’s more, the issue unites the GOP when the party is fractured among competing presidential contenders.

In the poll, Obama lags the two leading Republican rivals in the 12 states likely to determine the outcome of a close race in November:

•Former Pennsylvania senator Rick Santorum tops Obama 50%-45% in the swing states. Nationwide, Santorum’s lead narrows to 49%-46%.

•Former Massachusetts governor Mitt Romney edges Obama 48%-46% in the swing states. Nationwide, they are tied at 47% each.

Gallup has a separate poll on the question of repealing ObamaCare that shows a 47/44 split in favor of repeal.  This, however, is a poll of general-population adults.  USA Today’s poll was conducted among registered voters, and the negatives are much stronger.  Nationwide, it’s seen unfavorably by 50% of voters, as opposed to 42% who see it positively.  In swing states, it gets slightly worse ratings at 38/53, which is exactly the same percentages on Rasmussen’s repeal question from earlier this month. Pluralities of of 42% in swings states and 41% nationwide expect ObamaCare to make things worse for their families.

The most interesting aspect of the matchups is that Obama now scores below Republicans even though he faces no primary challenge.  Don’t forget that head-to-head matchups at this stage of the process is a bit of an apples-to-oranges comparison, thanks to the natural division among Republicans and independents during the primaries.  It’s a deeply significant sign that Obama can’t rise above his divided competition despite the battles taking place in the opposition party, and ObamaCare significantly drives that — even as Obama continues to campaign on his “achievement.”

Don’t forget one last thing, too. Democrats purposefully front-loaded the benefits of ObamaCare in 2010 in a desperate attempt to avoid a beating in the midterms.  ObamaCare won’t get any more popular between now and the election, and it’s likely to get less popular.