A Tea Party member reaches for a pamphlet titled "The Impact of Obamacare" at a "Food for Free Minds Tea Party Rally" in Littleton, N.H., in 2012. (Jessica Rinaldi/Reuters)

When the Affordable Care Act was signed into law, Vice President Biden famously intoned (on a hot mike) that it was a "Big f***ing deal."

For Democrats on the campaign trail, though, supporting Obamacare isn't really their deal.

According to an extensive new research paper from the Brookings Institution's Elaine C. Kamarck and Alexander R. Podkul, only 36 percent of Democrats running for Congress this year have expressed a position in support of Obamacare.

Another quarter (25.5 percent) of Democrats have offered a nuanced position that wasn't clearly in support of the law or against it, while 1 percent outright opposed it and 37 percent have offered no opinion.

The numbers were drawn from an exhaustive (and surely, exhausting) study of 1,662 candidates running in House and Senate primaries.

For comparison's sake, the GOP is overwhelmingly united against Obamacare, with 74 percent of candidates expressing opposition and only 5 percent preferring a more nuanced approach. Just 0.13 percent of GOP candidates supported the law.

The study also tested immigration, taxes, spending, climate change, the minimum wage and government regulation. On none of these issues were one party's candidates as conflicted as Democrats were on Obamacare.

Here's the chart on climate change, where a few Republicans have expressed a middle-ground approach but Democrats are much more united than on Obamacare:

And here's comprehensive immigration reform, where the same dynamic holds on both sides:

One might expect Democrats who hedge on Obamacare to belong to the more moderate wing of the party. And that's partially true, as 40 percent of Democrats identified by Kamarck and Podkul as "moderate" (again, this was a HUGE undertaking) had a nuanced position on Obamacare, while 25 percent supported it outright.

But even among so-called "progressives" — a.k.a. liberals — 31 percent offered something of a muddled position, while less than half — 48.5 percent — were clearly in support.

One caveat on all this: We're guessing many candidates for Congress didn't have much in the way of a campaign or paper trail. Hence the prevalence of "no information" candidates in the graph above. This is true across all issues. But the split between support and "complicated position" is still pretty stark.

We would also note that the vast, vast majority of the Democratic candidates for Congress are not running in competitive states and districts in which you would expect them to be gun-shy about supporting Obamacare. In fact, many more of them faced contested primaries in which you would think supporting Obamacare might be a good thing.

And still, very few have run on President Obama's signature legislative achievement.