Another leading presidential super PAC signaled Thursday that it plans to keep its donors' identities under wraps until Jan. 31, meaning voters in four crucial early contests will go to the polls without knowing who is behind two well-funded efforts to influence their decisions.

Winning Our Future, an outside group backing Newt Gingrich, notified the Federal Election Commission that it is changing its filing status to push back a deadline for making donations public by four weeks, copying a move made earlier this month by Restore Our Future, a group backing Mitt Romney, one of Gingrich's chief rivals for ...