Six months after Kathy Hochul suddenly became New York’s first female governor, the Democratic State Convention on Thursday showcased just how much the political dynamics of the state had changed since Andrew M. Cuomo’s stunning resignation.

Ms. Hochul has quickly cemented institutional Democratic Party support, reflecting both the advantages of incumbency and a meticulous and relentless personal political effort, and the party was expected to endorse her later Thursday. Hillary Clinton, the first female presidential nominee of a major political party and a former New York senator, was slated to introduce Ms. Hochul, marking the most high-profile day of campaigning yet for the governor as she runs for a full term.

The convention capped an extraordinary year in New York politics, defined in New York City by the election of the city’s second Black mayor, Eric Adams, and in Albany by the ouster of Mr. Cuomo amid ​​allegations of sexual harassment and misconduct.

Attorney General Letitia James, who briefly challenged Ms. Hochul but is now seeking re-election, released an investigation into Mr. Cuomo’s conduct that led to his resignation. He has denied touching anyone inappropriately and, emboldened by decisions from top prosecutors to rebuke but not to prosecute him, he has signaled to associates that he hopes to regain relevance in public life.

In an enthusiastically received appearance before the convention, Ms. James defended the report and lashed Mr. Cuomo.

“It has become clear that the former governor will never accept any version of these events other than his own,” she said. “To achieve that, he is now claiming the mantle of victim and disgracefully attacking anyone in his path. Pushing others down in order to prop himself up. But I will not bow. I will not break.”

The crowd began to applaud, a stark reminder of how far Mr. Cuomo has fallen. Four years ago, the Democratic convention was a coronation for him, after a spirited primary challenge from the actress Cynthia Nixon.

Now he is a pariah among the party officials over whom he once wielded enormous influence.

“I will not be bullied by him,” said Ms. James, whose office is also conducting a civil inquiry into former President Donald J. Trump and his family business. “Or Donald Trump,” she added.

But much of the day was focused on the current governor.

“The party should be unified,” said Assemblywoman Rodneyse Bichotte Hermelyn, the chairwoman of the Brooklyn Democratic Party, who said she believed Ms. Hochul’s Democratic opponents — the New York City public advocate, Jumaane D. Williams, and Representative Tom Suozzi of Long Island — should drop out of the race. “These are great candidates, formidable candidates who take on great leadership roles, but it’s very clear and obvious that the vast majority of the people are behind Kathy Hochul. So why create fights?”

Mr. Williams is running to Ms. Hochul’s left, while Mr. Suozzi is waging a centrist campaign focused heavily on combating crime. Both lag her significantly in fund-raising and in the sparse public polling that is available; yet both argued on Thursday that they saw pathways that were not reliant on state party support.

“We all know that it’s kind of pageantry in here,” Mr. Williams said. “It’s set up for the incumbents. So we all know pretty much how this is going to go.”

Ms. Hochul is unquestionably the clear front-runner. Other races, though, appeared even less competitive. After years of speculation concerning whether the Senate majority leader, Chuck Schumer, would face a credible left-wing challenge, he was renominated for his seat by acclamation on Thursday.

Attention on a potential primary challenge had long focused on Representative Alexandria Ocasio-Cortez, a left-wing leader and Democratic congresswoman from New York, but she confirmed in an interview recently that she was running for re-election. And the first person to nominate Mr. Schumer on Thursday, the Brooklyn borough president, Antonio Reynoso, is a prominent younger left-leaning official.

“I love New York,” Mr. Schumer declared. “I love representing New York as Senate majority leader. I’ll love it even more when we pick up two more seats.”

But the convention arrived toward the beginning of a midterm campaign season that appears brutally difficult for the Democratic Party nationally, and potentially challenging even in liberal New York. The party sustained major losses on Long Island and even in a few New York City races in November.

Mr. Suozzi alluded to some of the party’s challenges during a Thursday breakfast.

“We are not speaking to the issues that the people are concerned about,” he said, laying out a centrist vision that includes fighting crime, grappling with high property taxes, focusing on the environment and improving schools. “We’re not resonating.”

He also proactively acknowledged the institutional resistance he faces, noting the prominent Democrats who have questioned why he would give up his seat in Congress to run.

“I spoke with our keynote speaker today, Hillary Clinton, a few months ago, she tried to persuade me not to run,” he volunteered. But in his speech and in additional interviews, he said he saw a path forward and intended to release a new commercial this week. He has also named Diana Reyna, a former city councilwoman from Brooklyn, as his running mate.

“My intention is to get people to know who I am,” he said.

Mr. Williams, for his part, noted that he received around 47 percent of the vote when he ran against Ms. Hochul for the lieutenant governorship in 2018. As endorsements come together and more voters tune into the race, there is still time for him to catch fire, he said — though whether he can get his message out effectively when he trails Ms. Hochul in fund-raising by around $21 million is an open question.

“New Yorkers are just now starting to wake up,” he said.

Another point of tension evident at the convention was concern around Latino representation; a preliminary schedule listed no Latino speakers, though some were added later.

Representative Adriano Espaillat, a New York Democrat, pointed out that it was Ms. James, not state party leaders, who invited him to introduce her as the party’s choice for attorney general. “It’s critical that the Democratic Party be sensitive of Latino voters,” he said. “I think that’s a great challenge for the party.”

Jay Jacobs, the chairman of the New York State Democratic Committee, suggested the party had not needed to invite speakers whom candidates had already reached out to and argued that some of the outcry was around a preliminary list that didn’t represent the full diversity of the speaker slate.

“We have to be sensitive,” he said. “We have to be careful, and I certainly don’t want to offend anybody, and we’ve been working very hard not to do that. But I’m sure that if you look hard enough, we’re going to make a mistake here and again.”

Grace Ashford contributed reporting.