Republican presidential candidate Mitt Romney visits St. Paul's Lutheran Church while campaigning in Berlin, N.H., on Dec. 22, 2011. Did Romney's Mormon ties work against him in the 2012 general election? Among Democratic-leaning voters, possibly so. (Charles Krupa/AP)

It's probably no surprise that, in the United States, the two most unpopular religions are Islam and atheism (to the extent atheism is, you know, actually a religion).

And new data from the Pew Religion and Public Life project show that is indeed the case. The average rating for these two groups, on a scale of zero to 100 (with 100 being the best), is around 40.

Here's how that looks, compared to other religions:

But where it gets interesting is when you introduce politics into the mix.

Among Republicans and GOP-leaning Americans only, atheists and Muslims are still the least-popular religion -- and even more so than among the general population. But among Democrats and Democratic-leaning Americans, the most unpopular religion is ... wait for it ... Mormonism!

What explains this? Politics, of course.

Mormons, as you probably know, are among the most conservative Americans. A recent Pew study showed they favor Republicans over Democrats by a 65 percent-to-22 percent margin. Mormons are also harder on President Obama than any other religious group, with 78 percent of them disapproving of Obama's job performance, according to a Gallup poll last week.

There's also the matter of the most recent GOP presidential candidate having been an adherent of the Mormon faith. Remember that?

In other words, it's pretty clear that, when it comes to partisans' views of different religious groups, politics play a pretty major role.

Democrats also, notably, rate the heavily conservative evangelical Christian faith (53) much lower than Republicans do (71). In fact, when you exclude evangelical Christian Democrats from the survey, views of evangelicals drop to 45 -- almost as low as Mormons and lower than Muslims.

And it doesn't just work in reverse. Muslims, as we noted last week, vote heavily Democratic and are actually Obama's best religious group, according to that same Gallup study.

We're not sure a lot of Democrats know that Muslims are on their political team, but that likely buoys support for a religion that many Americans continue to have reservations about 13 years after the terrorist attacks of Sept. 11, 2001.