The latest Iowa Poll by The Des Moines Register finds Gov. Chet Culver losing to both former Gov. Terry Branstad and Sioux City businessman Bob Vander Plaats in hypothetical head-to-head campaigns.

Culver’s job approval rating, at 40 percent, has hit the lowest point since taking office and has dropped 20-percentage-points since January. In a head-to-head matchup with several potential GOP challengers, Culver loses to Branstad 57 percent to 33 percent. An October poll conducted by Research 2000 had Branstad beating Culver 48 percent to 43 percent.

In the October poll, Culver bested other Republicans by at least 20 points. But in the latest Register poll, Vander Plaats beats him 45 percent to 37 percent.

The governor doesn’t reach 50 percent against any Republican opponent, but does defeat state Rep. Chris Rants and Cedar Rapids businessman Christian Fong.