Contemporary anti-Mormonism tends to emerge either from the secular left or from the evangelical Protestant right. For the left, Mormonism often functions as a stand-in for discomfort over religion generally. Mormon religious practice offers a lot of really, well, religious religion: ritual underclothing, baptism for the dead, secret temple rites and “clannishness” (a term invoked in the past in attacks on Catholics and Jews). Any religion looks weird from the outside, but the image of Mormonism seems caught somewhere between perpetual strangeness and strait-laced blandness.

When a perceived oddity is backed by Mormon money or growing political clout, the left gets jumpy. MSNBC’s Lawrence O’Donnell and HBO’s Bill Maher have resorted to caricature, stereotyping and hyperbole in their anti-Mormon attacks. Liberals were outraged by Mormon financing of Proposition 8, the 2008 ban on same-sex marriage in California. They scoff at Mormonism’s all-male priesthood and ask why church leaders have yet to fully repudiate the racist teachings of previous authorities.

For the right, Mormonism figures in even more complicated ways. The Mormon road to respectability has often led, as it did for Mr. Romney, through Harvard Business School; pro-business Republicans have found ready friends among well-placed Mormons. But many rank-and-file evangelical Protestants call Mormonism a cult — as the pastor Robert Jeffress did last fall — or a “non-Christian religion.” Indeed, evangelical hatred has been the driving force behind national anti-Mormonism.

The brief “golden age” of Mormonism’s positive image — roughly 1935 to 1965, according to Jan Shipps, perhaps the leading non-Mormon scholar of the Latter-day Saints — coincided with a period of conservative Protestant retreat. Embarrassed after their fight with modernists in the mid-1920s, evangelical Protestants withdrew from public engagement, built their own impressive church and educational networks, and re-emerged in the 1970s as a formidable force on the political right. The subsequent “countercult” movement within evangelicalism targeted Mormonism with gusto.

Anti-Mormon attacks by evangelicals have betrayed anxiety over the divisions in their movement and their slipping cultural authority as arbiters of religious authenticity. Some big-hearted evangelicals have recently reached out to Mormons with genuine understanding, but they must now fend off charges of getting too cozy with Satan’s minions. Because evangelicals are hard pressed for unity to begin with, and because they have defined themselves less and less in terms of historic Christian creeds, their objections to Mormonism might carry less and less cultural weight.