Former House Speaker Newt Gingrich hinted Sunday that if rival Republican presidential candidate Mitt Romney loses the primary election in his home state of Michigan, he should drop out of the race. “If he loses his home state, I don’t see what he says the next morning to his donors to stay in the race,” Mr. Gingrich told “Fox News Sunday.” If Mr. Romney, a former Massachusetts governor, can’t win his home state in a primary election, how can he beat President Obama in Michigan, which typically votes with the Democrats, Mr. Gingrich asked.