Newt Gingrich will officially pull the plug on his presidential bid Wednesday, marking the end of a roller-coaster candidacy that dove into and out of debt — and into and out of contention during the bloody Republican nomination race.

In a hat tip to supporters, the Georgia Republican released an “insider advance notice” online video Tuesday, in which he thanked them for their support and urged them to do all they can to stop President Obama from winning a second term in the November election.

“A re-election of Barack Obama will be a genuine disaster, and all of us have an obligation, I think, to do everything we can to defeat Barack Obama,” Mr. Gingrich said, vowing that he and his wife, Callista, will continue campaigning to defeat Mr. Obama. “I hope you will join us in this historic effort, because this is still the most important election in our lifetime.”