Slight pause. Sly grin. “I’m just kidding!” she said.

The members of her caucus cracked up, releasing years of frustration, their heads swinging back with joyous laughter. Ms. Stewart-Cousins threw up her hands like a champion, clapped and shouted, “Yay!”

These heady times at the Capitol have some of New York’s liberals pinching themselves. Susan Lerner, the executive director of Common Cause New York, a reform group, said she was recovering from shock after watching Democrats in the first hours of the new legislative session pass voting reforms that had been stymied for years. “It’s whiplash,” Ms. Lerner said. “Is there more to do? Yes. But today, we’re celebrating.”

On an Amtrak train taking chattering lobbyists, aides, journalists and lawmakers to Gov. Andrew Cuomo’s annual budget address on Tuesday, the progressives on board were giddy, a strange feeling for them on a trip to Albany in January. “I’m jazzed,” said the New York Civil Liberties Union’s executive president, Donna Lieberman. She joked that in previous years she’d often felt like she needed to take a shower after spending time in the State Capitol.

Less jazzed were Senate Republicans, who after decades of uninterrupted power, now seemed vaguely lost. On Tuesday, for example, they suggested that if marijuana must be legalized, any revenue should go to a tax cut. Good luck with that.

For some Republican lawmakers, a vote for a bill that would treat violence against transgender individuals as the hate crime that it is seemed particularly hard to take. From their seats in the back of the room, a couple of the Republicans rolled their eyes and snickered.

At one point, State Senator Jessica Ramos, one of six members who won primaries against turncoat Democrats who had caucused with Republicans, said lawmakers should go even further to help transgender New Yorkers, leading State Senator Frederick Akshar, a Republican, to exclaim: “Jesus Christ! Further?”

Even for Democrats, though, it hasn’t been all fun and reforms.

In the Assembly, Speaker Carl Heastie marred an otherwise banner start to the new year by engaging in a legal maneuver to try to keep a $50,500 pay raise for lawmakers while eliminating limits on outside income set by a special committee that enacted the raise. No doubt he has better ways to spend his time.