Just a couple of weeks into his new job, Virginia Attorney General Mark R. Herring has stirred a hornet’s nest with a decision that may or may not have contradicted a campaign promise that may or may not have contributed to the razor-thin margin by which he was elected over his Republican rival, Mark D. Obenshain.

Herring, who won the election by 957 votes after a recount, announced last week that he would not defend Virginia’s constitutional amendment defining marriage as an institution between one man and one woman. Then, he filed a brief in support of the plaintiff in a federal lawsuit seeking to overturn the amendment, which 57 percent of Virginians supported in 2006.

Despite the fact that earlier in 2006 he had voted in favor of putting the amendment before voters that November, and despite his reported support for that amendment in September of that year, Herring said last April — in the midst of his campaign for statewide office — that he “would work to change the law prohibiting such marriages.” Later, according to the Virginian-Pilot, he said “that his job, if he is elected attorney general, would require him to try in good faith to find a basis to defend the amendment’s legality,” a duty, the newspaper added “that he has pledged to fulfill.”

So maybe he’s fulfilled a campaign promise, and maybe he’s broken it.

But a group of legislators, including Suffolk’s Chris Jones, who serves in the House of Delegates, has called on Gov. Terry McAuliffe to appoint a special counsel to do what Virginia’s attorney general has refused to do: defend a constitutional amendment properly enacted by the legislature and the electorate.

Herring claims an evolution of his position from supporter of traditional marriage to supporter of homosexual marriage. And just weeks after taking office, he claims he can find no good-faith basis on which to defend the law.

Does this mean his prior position on marriage was not a good-faith position? Was President Obama, a fellow Democrat, speaking with anything other than good faith when he proclaimed during his own 2010 election campaign that he believes states have a right to decide the issue of homosexual marriage for themselves? Judging from Herring’s contention that Virginia’s ban on gay marriage violates the U.S. Constitution, one can legitimately wonder about the answers to those questions.

Herring has left defense of the Constitution of Virginia in the hands of the clerks of court in Norfolk and Prince William County, the two municipalities that have been sued in federal court.

Whatever his campaign promise regarding marriage, his promise to defend the Constitution of Virginia should be sacrosanct. If the attorney general is unwilling to keep that promise, Virginia’s new governor should demonstrate his respect for that document — and for the people who enacted it — by acceding to the request for a special counsel.