In a decisive rebuke to efforts by Democrats to dominate both houses of the New York State Legislature, voters elected Republicans to a clear majority in the State Senate on Tuesday, handing them a wave of victories upstate and on Long Island, and returning the party to full control in a chamber it long dominated.

The Republicans’ victories came despite energetic efforts by Mayor Bill de Blasio of New York City and United States Senator Charles E. Schumer to rally Democratic voters in a midterm election that boded badly for their party. Democrats have long held sizable numeric advantages in the State Assembly but have been thwarted in efforts to win control of the Senate, which is currently led by a coalition of Republicans and a five-member group of breakaway Democrats.

Earlier this year, Democratic Party leaders in Albany seemed confident that a clear majority in the 63-seat Senate was within reach, particularly after Gov. Andrew M. Cuomo made a commitment, after a challenge from the left last spring, to help fight for that goal.

Image State Senator Cecilia F. Tkaczyk in 2013. Credit... Nathaniel Brooks for The New York Times

But after winning his primary in September, Mr. Cuomo proved to be a less-than-energetic campaigner for Senate Democrats, sparing in his endorsements and rarely stumping for embattled incumbents or hopefuls. And on Tuesday, it seemed likely that the liberal wing of the Democratic Party would lay heavy blame at the feet of the governor, who was easily re-elected to a second term.