Getting the needling nature of such a maneuver may require a little context: In July 2013, Mr. Cuomo, faced with a barrage of corruption charges and convictions in the Capitol, proposed a Moreland Commission “to probe systemic corruption and the appearance of such corruption in state government, political campaigns and elections in New York State.”

It did not work out that way: The following spring, Mr. Cuomo abruptly shut down the commission at the tail end of budget negotiations, saying the Legislature had passed the ethics proposals he had wanted.

Government watchdogs were furious, and federal prosecutors — including the United States attorney at the time, Preet Bharara — were troubled, even more so when an investigation by The New York Times revealed that Mr. Cuomo had interfered in the workings of the commission. It was not until early 2016 that Mr. Bharara said Mr. Cuomo would not face federal charges over his handling of the commission, but the political and public relations damage to the governor had already been done.

The strategy of attacking an incumbent’s missteps is a political staple as old as Monday night fund-raisers, and carries with it a certain risk for Ms. Nixon: While she has proved adept at goading Mr. Cuomo — just last week, she basically taunted the governor, “What’s it going to be, Andrew?” while calling for a one-on-one debate — she risks being seen primarily as an antagonist, rather than a progressive leader of her own making.

In the coming months, Ms. Nixon needs to convince voters that she can manage the unwieldy state government, its forest of official policies and its labyrinthine legal framework. (Her announcement on Moreland contains two legal citations about the powers vested in such a commission, which date from 1907.)