A new poll from Virginia, a key swing state, suggests that evangelicals will help put Mitt Romney in the White House this November.

It has become a truism in recent years that evangelicals are critical to our national elections. As New York Times reporter Erik Eckholm pointed out on April 14, evangelicals accounted for nearly one-fourth of all ballots cast in recent presidential elections. Their lukewarm support for John McCain in 2008—with many staying home on Election Day and upwards of 30 percent of their 18-29 year-olds casting votes for Obama (Greenberg Quinlan Rosner Research)—helped give the White House to the Democrats.

Republicans have feared that Romney’s Mormonism will mean even fewer evangelical votes for their...