Emily’s List, the fund-raising juggernaut dedicated to electing women who back abortion rights, plans to throw its support on Thursday behind Gov. Kathy Hochul’s campaign for a full term as New York governor.

The group’s endorsement opens doors to deep-pocketed donors and seasoned campaign strategists across the country. But for Ms. Hochul, the state’s first female governor, it may prove more valuable as an early stamp of approval for female activists, donors and operatives as she attempts to freeze out potential rivals and head off a raucous Democratic primary next year.

In its endorsement, Emily’s List planned to cite Ms. Hochul’s management of the ongoing Covid-19 pandemic, as well as steps she has taken since assuming office in August to clean up a culture of intimidation and harassment that flourished in Albany under her predecessor, Andrew M. Cuomo.

“Governor Hochul stepped up to lead New York in a moment rife with skepticism and mistrust for Albany,” said Laphonza Butler, the group’s president. “As governor, she has prioritized rebuilding trust between her administration and New Yorkers, and delivering results.”

The timing of the endorsement by the group, known for making shrewd calculations about who it thinks can win, was conspicuous. It is likely to make ripples through the large field of high-profile Democrats mulling campaigns, including the state attorney general, Letitia James, who would be the first Black woman elected governor of any state.

In backing Ms. Hochul before others decide whether to enter the race, the group appeared to simultaneously signal that it believed she was the candidate best positioned to win and do its part to help keep others out of the race.

The endorsement stood in sharp contrast to many of New York’s most influential unions, campaign donors and other elected leaders, who appear to be withholding support until it becomes clearer whether Ms. James and other Democrats — including Mayor Bill de Blasio, Representative Tom Suozzi or Jumaane Williams, the New York City public advocate — decide to run.

The decision may be particularly stinging for Ms. James, who is generally viewed as Ms. Hochul’s most formidable potential opponent and whose investigation into claims of sexual harassment prompted Mr. Cuomo to resign. Emily’s List endorsed Ms. James’s campaign for attorney general in 2018, touting her as a candidate who “always had the back of every New Yorker, especially women.”

The group, however, has also endorsed Ms. Hochul in past races for lieutenant governor and for a seat in Congress.

In many ways, Ms. Hochul is a natural candidate for Emily’s List to back. She has been a stalwart supporter of abortion rights for decades, and achieved a historic first in a state that has resisted elevating women to some top offices.

Ms. Hochul, who is Catholic, has made abortion rights a priority of her young administration. After Texas last month instituted a ban on any abortions after six weeks, the governor declared New York a “safe harbor” for women from the state. She also vowed to implement New York’s 2019 Reproductive Health Act, including drawing up a patient bill of rights.

The endorsement is the latest sign that Ms. Hochul, the only Democrat who has formally entered the race for governor, is moving swiftly to amass resources and support in hopes of altering the shape of the primary field.

In recent weeks, she has locked down endorsements from the Democratic Governors Association, the chairman of the New York State Democratic Party, and nearly two dozen other leaders of party county committees. She has hired a campaign manager and key consultants. And she has set a blistering fund-raising pace to try to raise $10 million or more by the end of the year from many of the state’s largest political donors.

So far, the hard-charging approach, coupled with Ms. Hochul’s performance as governor, appear to be paying dividends with voters.

A Marist College poll released on Tuesday showed Ms. Hochul with a considerable head-to-head edge over her potential opponents if the election were to take place today. But that could change should Ms. James or another candidate formally enter the race.