Letitia James, New York’s attorney general, is preparing to announce as soon as Thursday that she will run for governor, according to six Democratic leaders briefed on her plans.
Ms. James, her chief of staff and key political advisers began informing allies in the state’s labor unions and Democratic political circles in recent days that she intends to challenge Gov. Kathy Hochul in next year’s Democratic primary, and could make her plans public as early as Thursday, potentially by video.
Several of the Democrats, all of whom asked for anonymity to detail private conversations, said that the attorney general’s team was seeking commitments for early endorsements that could help build momentum for a campaign.
Ms. James’s team would not confirm early Wednesday afternoon that she intended to enter the race, but an adviser later said that a decision had been reached, ending months of deliberations.
“Attorney General Letitia James has made a decision regarding the governor’s race,” the adviser, Kimberly Peeler-Allen, said in a statement. “She will be announcing it in the coming days.”
Ms. James’s candidacy would ensure an expensive, high-profile Democratic primary that would set up a marquee test over the direction of the party in a heavily Democratic state. It will also establish a vigorously contested race that some party leaders had hoped to avoid after years of party infighting.
Ms. James, 63, would enter the primary as the most formidable challenger to Ms. Hochul, New York’s first female governor, who has taken an early lead in sparse public polling. The two were scheduled to appear on Wednesday evening at the same New York City reception for a group that supports women running for public office.
A former New York City Council member from Brooklyn, Ms. James has won citywide and statewide office and would offer voters the chance at another historic first: If elected, Ms. James could be the first Black woman ever elected governor in the United States.
As attorney general, she has won acclaim from liberals for taking on the National Rifle Association, investigating former President Donald J. Trump and overseeing the inquiry into sexual harassment claims against Andrew M. Cuomo that ultimately led to his resignation as governor. But it was not yet clear to allies or analysts how Ms. James would seek to differentiate herself politically or ideologically from Ms. Hochul.
“It’s going to be a definitive moment to have a sitting governor challenged by the current attorney general from the same party who are both history-making in their own right,” said State Senator Brad Hoylman, a Democrat from Manhattan, who cautioned he was not aware of Ms. James’s plans. “This is the beginning of understanding the differences in the candidates.”
The exact timing of Ms. James’s announcement appeared to still be up in the air on Wednesday. If she does not announce before the end of the week, her plans could collide with two major events on New York’s political calendar next week: New York City’s mayoral election and the annual conclave of the state’s Democrats in Puerto Rico.
One Democrat familiar with the attorney general’s thinking and deliberations said that Ms. James, who has considered the decision exhaustively, could still reverse course and either announce an exploratory committee for governor or that she will seek another term as attorney general rather than pursuing the top post. A late change of plans is not unprecedented in New York politics: Gov. Mario M. Cuomo famously abandoned airplanes waiting on the tarmac to whisk him to New Hampshire when he decided not to run for president in 1991.
So far this year, Jumaane D. Williams, the New York City public advocate, formed an exploratory committee last month. Another Black Brooklynite with appeal to some on the left, he could compete with Ms. James for key demographic and ideological constituencies.
Other Democrats are still considering runs, including Mayor Bill de Blasio in New York City and Representative Thomas Suozzi, an outspoken centrist from Nassau County.
Ms. James has been slowly positioning herself to run for weeks. She launched a statewide tour under the auspices of the attorney general’s office, meeting with local elected officials in far corners of New York. She has increased the ambitions of her fund-raising. And her political team has hired a handful of top-tier consultants, including Ms. Peeler-Allen and Celinda Lake, who served as one of the lead pollsters to President Biden’s 2020 campaign.
The James campaign’s courtship of some of the state’s largest public and private sector employee unions could be particularly important to building the kind of financial and political resources she would need to compete.
But the question of whether to run has been a uniquely complicated one for her. Ms. James would be giving up a powerful and secure position to run in a race she is not guaranteed to win, and some Democrats prefer her to stay in place as attorney general to see through existing cases, including one involving Mr. Trump and his businesses.
Ms. James and her advisers are also preparing themselves for an onslaught of attacks from Mr. Cuomo, who commands an $18 million campaign war chest and has indicated he may attempt to meddle in the race. Mr. Cuomo and his allies have characterized the attorney general report that led to his demise as politically motivated and influenced by Ms. James’s interest in running.
“I don’t think there’s any doubt that he’s manipulative and vindictive and knows that if she did not have the backbone to stand up as she did, he would still be governor,” said John Samuelsen, the international president of the Transport Workers Union, which has backed Ms. James in past campaigns. “He grinds axes with the best of them.”
As Ms. James deliberated, Ms. Hochul has been briskly fortifying her own campaign operation.
She has secured key endorsements from Emily’s List, the influential national group dedicated to electing women who support abortion rights, and Hazel Dukes, president of the N.A.A.C.P. New York State Conference. She has also raised gobs of money, bouncing from fund-raiser to high-dollar fund-raiser, including a reception hosted Tuesday night by Bolton St. Johns, the Albany lobbying firm, where tickets cost between $5,000 and $25,000.