Buoyed by an uptick in national polling, Donald Trump is expected on Wednesday to outline the reasons he still thinks he can win heavily Democratic New York as he accepts the small but influential Conservative Party’s nomination for president.

Trump, who will deliver an evening address as the Conservatives wind up their convention at the Marriott Marquis in Times Square, “thinks he can win New York, as difficult as that may seem to people out there, if the stars align correctly,’’ a senior Trump campaign operative told The Post.

“New York means a lot to Mr. Trump and he has not by any means given up on the state,’’ the operative said.

Longtime Conservative Party Chairman Mike Long told The Post, “I know how difficult it would be to win this state,” but he added Trump does have a shot.

“Trump’s numbers upstate are pretty good, and they’re pretty good on Long Island, so I don’t think it’s impossible that he could take New York. And I don’t see any real enthusiasm for Hillary Clinton out there, and that’s an indicator,’’ Long said.

A recent Siena College poll of New York voters found Clinton with a massive 30 percentage-point lead over Trump, but Trump campaign insiders insist the gap will close quickly if their candidate performs strongly in the upcoming debates.

Long conceded that several high-profile conservatives have refused to endorse the Trump campaign, but said he was hopeful they would reconsider.

“While I understand and respect the point of view of conservatives who have been opposing him, Trump is, in fact, the most conservative candidate running for president on a wide range of issues, including immigration, jobs, taxes, Supreme Court appointments and regaining our image as a world leader,’’ Long said.

The Trump campaign source said “tentative approval’’ has just been given to an ambitious New York strategy plan that calls for the opening of 10 campaign operation centers and the heavy use of phone banks, direct mail, and other get-out-the vote efforts.

Long Island Democrats are increasingly optimistic — thanks to a federal judge, Republican rivalries, and what they see as a lagging Trump campaign — that they’ll be able to hold on to the North Shore’s Third Congressional District seat being vacated by longtime US Rep. Steve Israel, the outgoing chair of the Democratic Congressional Campaign Committee.

Former Nassau County Executive Tom Suozzi, the Democratic contender who mounted an ill-fated challenge to Eliot Spitzer in the Democratic primary for governor 10 years ago, held a 16-point lead over state Sen. Jack Martins in a Democrat-sponsored poll released last month, but a federal judge delivered even worse news to Martins.

The jurist ruled that a resources-draining special Republican congressional primary must be held Oct. 6 because state judges, at the urging of longtime Nassau County GOP election lawyer John Ciampoli, had improperly denied long-shot challenger Philip Pidot the opportunity to challenge Martins in the regularly scheduled June 28 primary.

Stung by the ruling, Martins — in a rare maneuver that stunned many election lawyers — sought unsuccessfully to have a federal judge reschedule the congressional balloting from Nov. 8, the date of the general elections, to Dec. 6.

Martins has appealed the judge’s decision.