President Donald Trump continues accusing congressional Democrats of treason — a crime punishable by death — over their border security policies even as his acting chief of staff was on Capitol Hill Wednesday seeking a deal.

And a senior Democratic aide expressed doubt that a deal is likely over what promises to be among 2020’s most contentious campaign trail issues.

Twice on Wednesday, the president had critical words for Democrats over their ongoing dispute about his proposed U.S.-Mexico border wall and a list of other policy differences related to immigration. In a tweet as he returned from Texas on Air Force One, the president again accused unnamed Democrats of betraying their country — apparently for opposing his hardline immigration policies.

“I think what the Democrats are doing with the Border is TREASONOUS. Their Open Border mindset is putting our Country at risk. Will not let this happen!” Trump tweeted at 10:33 p.m. He hit send on the post five minutes before a reporter traveling with him said Air Force One landed at Joint Base Andrews outside Washington.

I think what the Democrats are doing with the Border is TREASONOUS. Their Open Border mindset is putting our Country at risk. Will not let this happen!

— Donald J. Trump (@realDonaldTrump) April 11, 2019

Trump’s use of the T-word is curious for many reasons, especially because policy differences with a sitting president are not criminal — much less a capital — charge. Another reason: His top spokeswoman recently panned Democrats over their contention that the Robert S. Mueller-led Russia probe would clearly show her boss colluded with Russians during the 2016 presidential campaign.

“They literally accused the President of the United States of being an agent for a foreign government. That’s equivalent to treason. That’s punishable by death in this country,” White House Press Secretary Sarah Huckabee Sanders told Fox News on March 25.

Trump is eager to make immigration a major part of his 2020 reelection campaign after the issue helped him win the presidency in upset fashion four years earlier. His late-night treason tweet came hours after he called on Democrats to help him and Republicans improve what he dubbed “bad laws” related to the southern border and immigration.

[Trump tries to revive North Korea talks in meeting with South Korea’s Moon]

“It’s very important that the Democrats in Congress change these loopholes,” the president said Wednesday morning as he left the White House for the Lone Star State before issuing a warning: “If they don’t change them, we’re just going to be fighting.”

As often is the case, Trump recently has signaled he is pivoting toward, in his words, a “tougher” immigration and border security stance. He has removed several senior Department of Homeland Security officials, including former Secretary Kirstjen Nielsen.

Last Friday, the White House withdrew the nomination of Ron Vitiello to lead the Immigration and Customs Enforcement. “Ron is a good man, but we’re going in a tougher direction,” Trump said.

On Friday at the border in California, Trump said this to would-be migrants: “The system is full. We can’t take you anymore. … Our country is full.” This has left Democrats outraged.

But as Trump moves to the right yet again in his public remarks about the border and immigration — including signaling Tuesday that he views his since-scrapped child separation policy as an effective deterrent to illegal immigration even though he is not restarting it — his top aides are looking for a path toward a bipartisan deal.

Acting Chief of Staff Mick Mulvaney, a former conservative GOP congressman from South Carolina, was on Capitol Hill on Wednesday meeting with senators of both parties.

Those talks were border-related, a source with knowledge of the meetings said, acknowledging the White House is trying anew to strike a deal amid a dramatic upswing in illegal border crossings and apprehensions that has left the president admittedly frustrated.

[Trump finally finds a Bush he likes: Texas Land Commissioner George P. Bush]

One senior House aide told Roll Call Thursday morning that among that chamber’s Democratic caucus, “no one views the White House as credible on this issue” because the president and his top aides are “constantly talking out of both sides of their mouths.”

The same Democratic source said there were no signs Mulvaney met with House Democrats on Wednesday.

Neither Trump, congressional Republicans or congressional Democrats have explained any proposal that the other involved parties might support.

The Senate passed a bipartisan immigration overhaul bill in 2013. But it immediately stalled in the then-GOP controlled House. And when a group of Democratic and Republican senators in 2017 pushed a bipartisan measure, Trump himself helped sink it as his more-hardline version received even fewer votes.

The two parties have been in a standoff ever since, both playing a role in a partial government shutdown that bridged 2018 and the start of this year.

That longest shutdown in U.S. history culminated in Trump getting less for his proposed border barrier than he could have gotten in the weeks before those handful of agencies, including DHS, were shuttered.

There has been no movement since. Instead, there have been just words like “treason” being bandied about by the president while Democrats continue to label his border barrier as a waste of taxpayer money and his immigration stances un-American.

House Speaker Nancy Pelosi of California told reporters at a Democratic retreat at a Leesburg, Va., resort said she remains “optimistic” about a deal.

“It’s complicated but it isn’t hard to do if you have good intentions,” Pelosi said of a comprehensive immigration overhaul agreement. “And I’m not giving up on the president on this.”

Lindsey McPherson contributed to this story.