TRENTON, N.J. — Mayor Giuliani and Senator Clinton hold commanding leads on their home turf and are poised to sweep tri-state presidential primaries in New York, New Jersey, and Connecticut on February 5, a new poll shows.

A Quinnipiac University poll released today indicates the two leading contenders could pick up significant numbers of tri-state delegates for their respective party conventions.

Twenty states are holding presidential primaries February 5, which could determine each party’s nominee historically early in the process.

Mr. Giuliani and Mrs. Clinton “can count on their Northeast neighbors to give them an early bumper crop of delegates,” a director of the Quinnipiac University Polling Institute, Maurice Carroll, said.

Mr. Giuliani has three times the support of his nearest competitors, a former Tennessee senator, Fred Thompson, and Senator McCain, for the Republican nomination in all three states, according to the poll.

Mr. Giuliani leads Thompson, 45% to 12% in New York and 48% to12% in New Jersey, and he tops McCain, 42% to 14%, in Connecticut, according to the poll, which surveyed voters simultaneously in the three states.

In New York, Mr. McCain is third with 9%. In New Jersey, he ties for third with 12%, and in Connecticut Mr. Thompson is third with 10 percent.

With the Republicans’ winner-take-all primary rules, Mr. Giuliani could win all 183 tri-state delegates, giving him 15% of the 1,228 he needs to secure the nomination.

Mrs. Clinton also enjoys wide leads in the three states. More than twice as many voters polled support her as her closest Democratic competitor, Senator Obama.

The New York senator leads Mr. Obama 49% to 12% in New York, 46% to 20% in New Jersey, and 43% to 16% in Connecticut, according to the poll.