ALBANY — A Siena College poll released yesterday showed the Senate’s Republican majority may hinge on two veteran Republican senators who are deadlocked with Democratic challengers in the districts they’ve represented for decades.

Republican Senator Caesar Trunzo, who has represented the 3rd Senate District in Suffolk County since 1972, led Democrat Brian Foley 46% to 40%. That’s a dead heat in the poll that has a margin of error of plus or minus over 4%.

Republican Senator Serph Maltese, who has represented the 15th Senate District in Queens since 1988, was favored by 42% — the same as Democrat Joseph Addabbo Jr.

The 61st Senate District, open because of a longtime Republican retired, is also close. Democrat Joseph Mesi had 40% of the vote to Republican Michael Ranzenhofer’s 38%.

The Republican party has a 31-29 majority.

Officials from both parties said the poll bolsters their case for the November elections.

A spokesman for the Republican Senate campaign, Joseph Conway, said voters made it clear in the poll that they care about economic and tax issues on which Republicans are running.

“Our own polls show that they are gaining ground and poised for victory,” Mr. Conway said.

The state Democratic Committee says the poll shows Republicans are losing ground.

“Voters in New York are ready for a change in Albany and ready for a Democratic State Senate that will work on their behalf,” a Democratic chairwoman, June O’Neill, said.

Republicans have held the Senate for more than 40 years. But Republicans argue they should be in the majority, the sole Republican bastion in Albany in which Democrats control the governor’s office, the Assembly majority, the comptroller’s office, and the attorney general’s office.