Control of the State Senate likely will be determined on Long Island on Election Day, with the most competitive battles expected in Nassau County.

The chamber now has 32 Democrats and 31 Republicans, but unusual alliances have allowed the GOP to maintain power. Sen. Simcha Felder (D-Brooklyn) caucuses with Republicans, while 5 other Democrats make up an independent conference that often works with GOP leadership.

There are nine Senate districts on Long Island, and a flip of even two of the four Nassau seats held by Republicans could cause the party to lose its tentative grip on the Senate majority.

With Sen. Jack Martins (R-Old Westbury) running for Congress, Democrats are aggressively seeking his seat in the 7th District, where enrollment figures are among the most favorable to the party on Long Island.

Democrat Adam Haber, an East Hills businessman who lost to Martins is 2014, is facing Republican Elaine Phillips, the Flower Hill Village mayor.

Buoyed by the potential for high presidential turnout, Democrats also are targeting two longtime Nassau incumbents: Sen. Carl Marcellino (R-Syosset) in the 5th District and Sen. Kemp Hannon (R-Garden City) in the 6th.

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Suffolk County Water Authority chairman James Gaughran, of Northport, is challenging Marcellino and Garden City lawyer Ryan Cronin is running against Hannon.

And while the 8th District seat of Sen. Michael Venditto (R-Massapequa) wasn’t initially considered in play, Democrats upped their efforts there late last month after Venditto’s father, Oyster Bay Town Supervisor John Venditto, was indicted on federal corruption charges.

John Venditto has pleaded not guilty.

Democrats are running John Brooks, a registered Republican from Seaford, against Michael Venditto, who is seeking his second term.

Also, Sen. Todd Kaminsky (D-Long Beach) is attempting to hold onto the 9th District seat he narrowly own in an April special election. He faces the same Republican opponent, attorney Christopher McGrath of Hewlett.

The races have generated heavy spending by both the Democratic and Republican senate campaign committees, a nod to the districts’r importance statewide.

Republicans gave $533,000 in October alone to Marcellino, Hannon and Phillips, state board of elections records show. Democrats spent $568,000 over the same period on behalf of Gaughran, Cronin and Haber.

Until Kaminsky’s win in April, the Republicans represented all nine Long Island senate districts for nearly six consecutive years.

The Suffolk districts remain friendly to the GOP, and Democrats are not seriously vying for any of them.

Following are the races for state Senate in Nassau and Suffolk Counties:

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--1st District

Gregory-John Fischer (D)

Kenneth P. La Valle (R, C, I, Ref.)

--2nd District

Peter N. Magistrale (D, WF)

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John J. Flanagan (R, C, I, Ref.)

--3rd District

John M. De Vito, Jr. (D, WF)

Joseph L. Fritz (WE)

Thomas D. Croci (R, C, I, Ref.)

--4th District

John R. Alberts (D)

Philip M. Boyle (R, C, I, Ref.)

--5th District

James F. Gaughran (D, WF, WE)

Carl L. Marcellino (R, C, I, Ref.)

--6th District

Ryan E. Cronin (D, WF, WE)

Kemp Hannon (R, C, I, Ref., Tax Revolt)

--7th District

Adam M. Haber (D, WF, WE)

Elaine R. Phillips (R, C, I, Ref.)

--8th District

John E. Brooks (D, WF, WE)

Michael Venditto (R, C, I, Ref., Tax Revolt

--9th District

Todd D. Kaminsky (D, WF, WE)

Christopher T. McGrath (R, C, I, Ref., Tax Revolt)

Laurence S. Hirsh (G)