After in the criminal case against the former coal mining executive Donald L. Blankenship, the United States attorney in Charleston, W.Va., said on Monday that he would resign.

The prosecutor, R. Booth Goodwin II, said in that he would soon return to private practice. But it did not take long for West Virginia’s political class to assume that the resignation of Mr. Goodwin, a Democrat whose family is among the most influential in the state, was a step toward competing in 2016’s race for governor.

In a telephone interview on Monday evening, Mr. Goodwin declined to confirm whether he would become a candidate and said, “There will be some time to talk about what my next steps might be.”

If Mr. Goodwin runs in May’s Democratic primary, he will be a late entrant to a field that includes Jim Justice, a billionaire whose campaign has promoted his record as a businessman with interests that include coal, and Jeffrey V. Kessler, the party’s leader in the State Senate. But Mr. Goodwin would be expected to mount a formidable campaign backed by his family, which includes a federal judge and a former United States senator.

“The Goodwin family has played the role of kingmaker in the past in a number of political campaigns, so they and their connections know how to raise money, know how to run a modern political campaign,” said Michael Plante, a political consultant who is not involved in the campaign for governor.

Mr. Justice’s campaign did not respond to a message. Mr. Kessler declined to comment.

The prosecution of Mr. Blankenship, who was chief executive of the Company when 29 workers died in , would almost certainly emerge as an issue in any campaign. Mr. Blankenship was convicted this month of a misdemeanor charge of conspiring to violate federal mine safety laws, but a jury acquitted him of three felonies.

While the decision to prosecute Mr. Blankenship could aid a Goodwin campaign among voters who have grown weary of the coal industry’s troubled safety record, it could also provoke strident opposition to Mr. Goodwin.

“There is no more dangerous combination than an ambitious prosecutor and a terrible tragedy,” Mr. Blankenship’s lawyer, William W. Taylor III, said in an email after the resignation was announced. “The pressure to bring charges against Mr. Blankenship was irresistible. There is no other explanation for a case so thoroughly unsupported by evidence.”