Gov. Andrew M. Cuomo on Saturday endorsed Thomas Suozzi's election challenge to GOP Nassau County Executive Edward Mangano as part of a broader call for Long Island voters to choose Democrats on Nov. 5.

At a rally with more than 200 Suozzi supporters in Albertson, Cuomo formally backed the former two-term county executive, who is seeking his old job back.

Cuomo's nine-minute speech focused on his administration's legislative achievements and why he says it is important for Long Islanders to elect Democrats. He described Suozzi as "Nassau's next county executive" at the end of his remarks as he recited the list of candidates he was endorsing.

The governor elaborated on the endorsement in interviews with reporters afterward. He described Suozzi as "a personal friend" he has known for 20 years. "I have supported him in the past and worked with him in many different capacities," Cuomo said. "He is tremendously talented."

Cuomo said voters should support Suozzi because he has a "Democratic platform . . . Our agendas are aligned."

Cuomo's endorsement ends months of speculation about whether he would back Suozzi. The governor has made several public appearances with Mangano recently.

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Stories have circulated for years that he was not close with Suozzi. But, Cuomo, who won Nassau County in the 2010 governor's race with 60 percent of the vote, said Saturday rumors about friction with Suozzi were false.

Cuomo declined to criticize Mangano, with whom he worked closely on the county's recovery from superstorm Sandy. "I work very hard to have good relations on both sides of the aisle," he said. "You can't play politics when it comes to running the government."

Accepting the endorsement, Suozzi hailed Cuomo as "one of the greatest leaders in the country" and said, "We share the same ideas, ideals and desire to serve the people." Suozzi was mentored early in his career by Cuomo's father, former Gov. Mario Cuomo.

Mangano spokesman Brian Nevin questioned the significance of the endorsement.

"With Andrew Cuomo endorsing every Democrat candidate in the state, it is clearly based on party line rather than accomplishments," Nevin said.

Mangano on Saturday debuted a new television ad with a video clip of Cuomo praising the Republican at a Lynbrook event shortly after signing the state's new property tax cap bill in 2011.

The clip shows Cuomo saying Mangano "believes in making government work for the people. He believes in putting politics aside for the good of this county."

Suozzi, however, said Mangano has "undermined" the property tax cap by failing to fix the assessment system, causing school taxes to skyrocket.

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Mangano on Saturday morning also joined 350 residents at the Epilepsy Foundation of Long Island's third annual walk and fundraiser at Eisenhower Park in East Meadow.

Mangano said money raised from the event would help the organization "reach out to elementary school students to teach them about epilepsy."