WASHINGTON—Rep. Ron Paul of Texas is the top presidential pick of the thousands of social conservatives who are meeting this weekend, winning 37 percent in a nonbinding straw poll.

Georgia businessman Herman Cain came in second at the Values Voters Summit in Washington with 23 percent, and former Sen. Rick Santorum of Pennsylvania placed third with 16 percent in Saturday's straw poll among the Republicans' White House contenders.

Rep....