To be honest, at this point whether some policy is "partisan" or not rarely has anything to do with its merits, and more about where it originates from, and how it's packaged. Just look at those studies when people were asked about "Obamacare" vs "ACA: (the latter has a lot more support, even on the right!).

So those razor-thin margins? They're not necessarily because the bill in question is not good. Indeed, the very politicians who vote against it might concede that it's good - in private. But they have elections to win, and voters to rile up to win them.

Not to mention that Congress, by design, is not really a good representation of public opinion. In fact, Senate is skewed so badly at this point that it's possible to pass and ratify a constitutional amendment through votes of politicians representing less than 1/4 of the country's population, so long as they're concentrated in the right states.