Republican presidential candidate Bill Weld is beefing up his New Hampshire campaign and urging Democrats there to re-register as “Undeclared” by Friday — so Granite State Dems can vote for him in the nation’s first primary against President Trump.

The former Massachusetts governor, after shaking hands Saturday at the Pumpkin Festival in Laconia, N.H., told the Herald his campaign is doing “everything we can to expand the electorate” for the Feb. 11 New Hampshire primary.

“The more the merrier,” Weld said.

Weld is making gains in New Hampshire, but he still has a long way to go. Trump has a 57-point lead on Weld, according to a new Franklin Pierce-Herald poll released this week.

Out of 402 likely Republican primary voters surveyed, 14% said they would support Weld, an 11-point rise from last month’s poll. Trump received 71% support in the latest poll, which is down 17% from the September survey.

“New Hampshire is obviously critical,” Weld said Saturday.

“We’re going to be a major presence in the final tally in New Hampshire,” he later added.

Speaking at a Tufts University presidential town hall this week, Weld outlined his strategy for cutting Trump’s support by winning primaries in New England and several Super Tuesday states, and enlarging the electorate by bringing more women and millennials to the polls.

Weld’s campaign on Friday announced the launch of an advertisement campaign ahead of the N.H. primary.

In the ad that will circulate in N.H. media outlets this week, the Weld 2020 campaign states, “Democrats. Republicans. Independents. Doesn’t matter. Governor Weld wants to earn your vote. A registered Democrat? You can re-register as an ‘Undeclared’ voter before Wednesday OCTOBER 25, 2019 … and cast your vote on February 11, 2020 for a different kind of leadership: A President America deserves.”

New Hampshire voters have a chance to send an early message in the Republican primary, Weld added.

“America deserves better, and I believe New Hampshire voters will lead the way,” he said.

But a longtime New England GOP strategist said it will be “very, very difficult” for any Republican to break through against Trump.

“It will be hard for any candidate to wrestle back the mainstream Republican voter,” Pat Griffin told the Herald. “You’re finding a lot of Republicans who will not participate in this race. The rest of them are Trump Republicans.”