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Mr. Duprey, who ran Sen. John McCain’s 2008 presidential campaign in New Hampshire, said the looming 2016 campaign may have something to do with the muted defense of Mr. Christie, as surrogates choose sides.

“If you are a friend of Gov. Scott Walker, for instance, you don’t want to do anything that promotes Gov. Christie over Walker,” Mr. Duprey said.

Mr. McDonnell and his wife, Maureen, were indicted Tuesday on charges that they accepted more than $135,000 in gifts — including private jet trips, vacations and loans — from a businessman.

Mr. McDonnell said he showed poor judgment but did not break the law and will fight the charges.

Mr. Christie, meanwhile, easily won a second term in the November election, but the honeymoon ended this month when emails seemed to indicate that members of Mr. Christie’s inner circle and some of his appointees at the Port Authority of New York and New Jersey were involved in engineering traffic jams on the George Washington Bridge in apparent retaliation for a Democratic mayor’s refusal to endorse the Republican governor’s re-election bid.

The federal government also launched a probe into Superstorm Sandy relief funds that were used to pay for tourism commercials starring Mr. Christie and his family during his re-election push, and a Hoboken mayor claims that the Christie administration threatened to withhold relief funds until the city supported a development project.

Mr. Christie has denied any wrongdoing on his part.