Associated Press
Republican presidential candidate, former House Speaker Newt Gingrich, waits in a holding room before speaking at a campaign stop Saturday, Feb. 18, 2012, in Suwanee, Ga.\r\n

WASHINGTON — Newt Gingrich said Sunday that he and other Republican presidential candidates must win their home-turf contests or face serious questions about continuing in the race.

The first test will come Feb. 28 in the GOP primary in Michigan, where rival Mitt Romney was born and his father was governor.

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If Romney loses in Michigan, "I don't know what he says the next morning to his donors to stay in the race," Gingrich told "Fox News Sunday."

But Gingrich also acknowledged that he must win the March 6 vote in Georgia, a state that launched his political career more than 30 years ago.

The same, he said, goes for Rick Santorum during the April primary in Pennsylvania, where Santorum was a senator.

"If any of the three loses our home state ... you have, I think, very, very badly weakened candidacies," Gingrich said.