Democratic Sen. Andrea Stewart-Cousins on Monday was formally designated the next majority leader in the state Senate by her colleagues in a conference that could have as many as 40 members at the start of the new year.

Sen. Mike Gianaris, a Queens Democrat, will return as the number two lawmaker in the conference and serve as deputy majority leader. Sen. Jose Serrano of the Bronx will serve as conference chairman.

There’s still some sorting out to do, including the naming of committee chairs and the question of whether Brooklyn Sen. Simcha Felder, a Democrat who is aligned with Republicans, will join the majority.

But the meeting of Democrats in Albany was a chance not just to take stock of next year, but make some history.

“This is a proud moment for me,” Stewart-Cousins said at a news conference shortly after the vote. “It’s certainly a moment that when I first came here I don’t think I ever dreamed of.”

The majority leader post in the state Senate is one of the most powerful positions in state government, holding sway over jobs, which bills come to the floor for a vote and a say in the budget talks.

Still, there are challenges.

She will lead one of the largest legislative majorities in the state Senate in decades, with members representing a range of constituencies from western New York to eastern Long Island.

Democrats have a full plate of long-sought legislative measures, including election reforms, the public financing of campaigns, the DREAM Act, gun control and a bolstering of abortion rights.

Potentially nettlesome issues include a single-payer health care measure several Democratic candidates campaigned on in support of, but Gov. Andrew Cuomo has been publicly cool toward. Asked about the bill on Monday in Albany, Stewart-Cousins said that issue, along with an extension of tax rates for upper income earners due to expire next year, is yet to be fully fleshed out by the conference.

“We’re not expecting collisions,” she said. “we’re expecting the opportunity to try and figure out the best way forward on these important issues to New Yorkers.”

And Stewart-Cousins will have a seat in the budget negotiations with Cuomo as well as Assembly Speaker Carl Heastie.

“New York is an incredible place — 20 million people. So much diversity,” she said. “Women uphold half of this state. The fact that there has never been a woman in the room was troubling.”

A working Democratic majority was not always a given.

The party had been out of power in the Senate for a decade following a disastrous two-year stint in control that was marred by a legislative coup. All of the previous leaders of the conference are virtually out of office and some are serving time in prison for corruption.

But the damage from the dysfunction was done, with five lawmakers splitting into a faction called the Independent Democratic Conference, which aligned with Republicans, allowing the GOP to maintain control even when they were outnumbered by Democrats.

The election of President Donald Trump, however, changed that arrangement.

The IDC dissolved earlier this year amid political pressure from Democratic activists and Cuomo, who had been accused of preferring the IDC-GOP alignment. All but two former members of the IDC won their primary challenges this year.

“I think we’re going to work well,” said Sen. David Carlucci, a former member of the IDC. “We’ve had more representation upstate and the suburbs than we’ve had before. It’s a conference that doesn’t just represent one part of the state, but the entire state.”