Americans' aversion to voting for Mormons has spiked since Mitt Romney's first presidential bid in 2007 — and the people most wary of Mormon candidates are not Evangelicals, but rather political liberals and non-religious voters, according to new research from a leading scholar of anti-Mormon attitudes.

The overall increase in anti-Mormon attitudes among liberals may be an unanticipated consequence of the "the continuing candidacy of Mitt Romney and Mormon activism against same-sex marriage," the study suggests. And its findings may be alarming to the Romney campaign because among the study's other findings is that voters' perceptions of Mormonism are closely tied to whether they'll vote for him.

According to American National Election Studies, nearly 35 percent of national respondents said in February they were "less likely" to vote for a Mormon. That's up nine points from 2007, when Pew found 26 percent of voters expressing concern about pulling the lever for a Latter-day Saint.

The uptick in anti-Mormon voter attitudes may come as a surprise to those who predicted Romney's candidacy would have a mainstreaming effect on his faith. But as University of Sydney scholar David Smith, the paper's author, writes, just as President Obama's successful candidacy didn't put an end to tense race relations in America, Romney's political assent hasn't cured the country of anti-Mormonism. In fact, as the data shows, Romney's rise may have lead to increased anxiety about his religion among his natural political opponents.

According to the paper, concern about Mormonism has remained relatively stable among Evangelicals, with 36 percent expressing aversion to an LDS candidate in 2007 and 33 percent doing so in 2012. But among non-religious voters, that number shot up 20 points in the past five years, from 21 percent in 2007 to 41 percent in February. There were also substantial increases in Mormon-averse voters among liberals — 28 percent in 2007 and 43 percent in 2012 — as well as moderates, who went from 22 percent in 2007 to 32 percent this year.

"Aversion to Mormons is still an important foce in American public opinion, and one that seriously affects Romney's chances even if he ultimately overcomes it," Smith writes in his paper, available online here.

Smith is the author of a detailed analysis on anti-Mormonism in the 2008 election, which suggested that the belief that Mormons aren't Christian was tightly linked to opposition to Romney among Christian conservatives.

The new study argues that the single most accurate predictor of how a voter views Romney is how he views Mormons — whether or not they are Christian, patriotic, hard-working, and friendly. Strikingly, the correlation between attitudes about Mormonism and support for Romney is even stronger than political ideology or party identification.

Perhaps most potentially distressing to Romney's campaign is the study's finding that conservatives who said they were less likely to vote for a Mormon were much more likely to say they were undecided or would not vote at all in a contest between Obama and Romney. Pundits have been predicting for months that anti-Mormon Republicans would stay home in November; this study reaffirms that idea.

The paper comes with an important caveat: the survey data was collected in late February and early March — in the heat of the Republican primaries. At that point, Romney was the clear frontrunner, but far from the presumed nominee. Since his opponents dropped out, Romney has earned plaudits from Republican operatives and activists for uniting the right behind him with his combative campaign style.

The two questions that remain are whether Romney can overcome Christian conservatives' deep-seated theological differences by taking the fight to Obama; and whether he can have to win over swing voters and moderates, whose perceptions of Mormonism have worsened over the past five years.