After wooing conservative Republicans on health care blew up in his face, President Trump is considering doing a total 180 and reaching out to congressional Democrats to get the rest of his agenda done.

"I think it's time for our folks to come together, and I also think it's time to potentially get a few moderate Democrats on board as well," Trump's chief of staff, Reince Priebus, told Chris Wallace on "Fox News Sunday."

Except, that's easier said than done. To have Democrats' ear, Trump will need to change pretty much everything about him — his tone, his substance, his policy — since he became president, say those very same Democrats in Congress.

"If he changes," Senate Minority Leader Chuck Schumer (D-N.Y.) said on ABC's "This Week," "he could have a different presidency."

Democrats saw a glimmer of promise in Trump's campaign rhetoric — he was critical of free trade deals, he was supportive of more taxes on the wealthy, and even at one point, he was open to a universal health-care system.

Trump says coming up with a bipartisan health-care bill will be 'so easy.' It won't be. (Peter Stevenson/The Washington Post)

But since Trump got inaugurated, he's dropped his populist streak and taken a hard tack to the right: He endorsed a health-care plan Democrats despised for its tax breaks on the wealthy and loosening mandated coverage for the poor. After his White House put out a travel ban 2.0 when the first one was stopped by the courts, Trump said at a campaign rally he wished the first could have stayed in place.

"He moved so far to the hard right that it's virtually impossible for us to work with him," Schumer said on ABC.

Then there's his cross-aisle negotiating style: Democrats say it's nonexistent.

To date, the White House has had substantial conversations with Democrats exactly zero times, top Democratic aides say. A classic example: Democrats found out about the White House's intention to work with them by watching Trump aides on TV Sunday, not by a phone call from the West Wing.

If Trump does call them up, Democrats feel like they have leverage to draw some red lines. Since controlling the House of Representatives, Republicans have not passed not one major piece of legislation without help from Democrats. Which means if Trump does decide that working with Democrats is his best path for an elusive legislative accomplishment, it could cost him dearly. Like:

On  health care:

Trump would have to give up his signature campaign promise, repealing Obamacare. "As long as they say, no more repeal," Schumer said on ABC. "That's a loser."

"And stop undermining ACA," he added, referring to the Affordable Care Act a.k.a. Obamacare.

On an upcoming deadline to fund the government:

There are a few things that Democrats say can't be in the short-term spending bill Congress must pass by April 28 to avoid a government shutdown, like:

No money to fund Trump's U.S.-Mexico border wall. (On late Tuesday, The Post's congressional team reported Trump does want Congress to add money for the wall.)

No cuts to federal funding to Planned Parenthood. (In a tweet Sunday casting blame on the health-care implosion, Trump suggested he's unhappy Planned Parenthood still has federal funds.)

And if you're going to increase defense spending, Democrats say, you need to increase domestic spending by a similar amount. (Trump's proposed budget calls for a massive 10 percent increase in spending to the military and equally sharp cuts to federal agencies — like eliminating 19 of them — to pay for it.)

On infrastructure:

This is probably the most promising positions for bipartisan compromise, since Trump's idea to invest $1 trillion to revamp infrastructure is more in line with Democratic principles on the government's role in the economy than Republican principles.

But Democrats submitted a plan to the White House nearly two months ago on how they'd like to get infrastructure done, and they have yet to hear back on it. They're concerned Trump would consider kick-starting infrastructure investment by giving tax breaks to developers to build roads — a no-no on the left.

On trade:

On trade, a good-faith act would go a long way, say Democrats. For example, Trump promised on day one of his presidency to label China a currency manipulator, a move he argues would force China to adhere to the same currency standards the United States does and thus make the trade playing field more even. (Many economists say that theory is outdated, but that's another story.)

For our purposes, Democrats point out that Trump could slap that label on China with the stroke of a pen, but he hasn't.

(We'll point out that shortly after taking office, Trump did use his pen to symbolically kill the already-dead Trans-Pacific Partnership, a deal most Democrats opposed.)

On taxes:

Here, the two camps are about as far apart as they can be.

This line from the Urban Institute and Brookings Institution's nonpartisan review of House Republicans' tax plan is a nonstarter: "Taxes would drop at all income levels in 2017, but most savings would go to the highest income households."

"There's not any Democrat that's going to vote for that," said Drew Hammill, a top aide for House Minority Leader Nancy Pelosi (D-Calif.)

Republicans' proposed border-adjustment tax, which would tax imports and exempt exports from taxes, is a nonstarter too, say Democrats.

What would pique Democrats' interest: Talking about cutting all or most of the $40 billion in tax breaks that the current tax code gives to oil companies to drill, for example.

Clearly, there's a lot of daylight between Trump and Democrats. But before they even get to a point where they're talking about policy, Democrats say the White House needs to start building its nonexistent relationship with them first.

"They need to change course and talk to Democrats," Hammil said. "And that doesn't mean sitting down in a room and throwing a bill at us and saying 'Take it or leave it.'"