Defying threats from President Trump, House Democrats on Friday unveiled their first bill for the new Congress — part of which would require Trump and future presidents to disclose their tax returns.

“We believe it will have great support,” Rep. Nancy Pelosi said, effectively thumbing her nose at Trump, who told The Post this week that he would declassify documents that would be “devastating” for Democrats.

“If they go down the presidential harassment track, if they want to go and harass the president and the administration, I think that would be the best thing that would happen to me,” Trump said during an exclusive Oval Office sitdown with The Post, using his term for congressional oversight of the executive branch.

“I’m a counter-puncher and I will hit them so hard, they’d never been hit like that.”

The documents include Justice officials’ request to surveil Trump campaign adviser Carter Page and memos on DOJ official Bruce Ohr’s interactions with Christopher Steele, author of a controversial dossier that alleged Trump ties to Russia.

Trump also wants to release text messages sent by former FBI officials James Comey, Andrew McCabe, Peter Strzok, Lisa Page and Ohr.

The Dems bill is a good-government package to limit big money in politics and make it easier for citizens to vote in addition to the tax return provision.

Trump is the first president in decades to not release his tax returns.

The legislation sets the tone for Democrats as they take the majority in January.

The bill would create automatic national voter registration while also expanding access to early and online registration.

It would increase federal support for state voter systems, including paper ballots to prevent fraud.

Political groups would need to disclose donors, and members of Congress would be barred from serving on corporate boards.

In a nod to Trump’s resistance to releasing his tax returns, the bill would require presidents to do so.

It also would create a Supreme Court ethics code.

Pelosi said it was more than a symbolic bill, but one they believe will have broad bipartisan backing.

“And that will not be lost on the Senate and the president of the United States,” Pelosi said.

Democrats who’ll be chairing top congressional committees next year say they won’t back down on investigating Trump because of his threats.

With AP