Democratic New York Governor Andrew Cuomo has endorsed the re-election of state Senator Stephen Saland, a Republican who backs gay marriage, prompting harsh criticism from Senator Ruben Diaz, the only Democrat in the New York Senate who voted against a bill legalizing such unions in the state.

Saland is among the four Republicans who last year voted to make New York the most populous state yet to embrace marriage equality.

Saland and Senator Mark Grisanti of Buffalo won their Republican primaries, while Senator Roy McDonald of Saratoga County was defeated. James Alesi of Rochester, the fourth senator, retired.

“The governor believes that one of the problems in our political system is the influence of extremists on both sides of the aisle,” the AP quoted a Cuomo spokesman as saying. “He is endorsing Senator Saland because he has consistently had the courage to do what was right despite political challenges, especially when it came to voting for marriage equality.”

Diaz criticized the move in an e-mail to supporters, saying Cuomo's endorsement “makes our victory as Democrats a real challenge.”

“You should know that the control of the New York Senate will be determined by the outcome of the November 6th General Election for State Senate races,” he wrote.

“I believe that Governor Cuomo is not only working against the Democratic Party as the leader – who as the leader should be protecting and defending the party and its candidates – but I also believe that he is working against racial equality and minority opportunities by preventing Black and Hispanics from gaining positions of leadership in New York State.”

It is the first Republican endorsement for Cuomo.