Barack Obama’s leading polling expert is also a member of an elite, invitation-only collection of liberal moneymen. Paul Harstad is a member of the Democracy Alliance, according to documents obtained by the Washington Free Beacon. The Alliance steers tens of millions of dollars to campaigns and groups backed by the White House, including the president’s Super PAC, Priorities USA, as well as to liberal nonprofits such as the Center for American Progress and Media Matters for America. Harstad is the closest direct tie between the administration and the secretive group, which does not disclose its members or donors. He has...