Mexico won’t pay for it. Democrats hate it. Border-state Republicans don’t like it. Congressional Republican leaders would rather not undertake it. There could be an avoidable government shutdown over it.

And yet President Donald Trump’s budget director is pushing Congress to spend $1.4 billion to start building his wall along the U.S.-Mexico border.

The political tension could backfire for the president. Trump’s insistence on a wall is increasingly doing what some had warned it would do: It’s undermining his relationship with Congress, it’s putting Republican leaders in a no-win scenario on whether to fund it and it could potentially derail the president’s ability to get anything else done.

Here’s why:

1. It’s building a wall between Trump and his party.

“Building a wall is the most expensive and least effective way to secure the border.”

That’s Rep. Will Hurd, R-Texas, whose district spans about 40 percent of the entire southern border, in a statement in January.

Hurd still doesn’t support it, nor – according to a recent survey of border-state lawmakers by Wall Street Journal – do any lawmakers in Congress who represent constituents on the border. That includes the Senate’s No. 2 Republican, John Cornyn of Texas.

Trump says his wall will “secure, protect and defend” Americans. But right now, he can’t even sell Republican lawmakers whose constituents would ostensibly benefit the most from it.

Pushing wary lawmakers to embrace the wall anyway risks further straining Trump’s relationship with his party, both with border lawmakers and with Republican leaders trying to avoid a shutdown next week. Speaking of …

2. It’s threatening a government shutdown.

Congress is facing a deadline of midnight Friday to pass a spending bill to keep the government open. Both Democratic and Republican leaders say they are successfully navigating the sinkholes that come with such a spending debate. (Similar political dynamics shut down the government in 2013 and very nearly in 2015.)

Funding Trump’s border wall has not been part of that bipartisan plan. It’s just too risky a debate to undertake when a government shutdown is on the line: Conservative Republicans are wary of the untold billions it will cost, border-state and basically all other Democrats oppose it. That’s more than enough opposition to kill any spending bill.

But the Trump administration has a different perspective. April 29 marks the president’s 100th day in office, and he badly needs a win. He’s looking to score one by getting funding for his centerpiece campaign promise. “We want wall funding,” Trump’s budget director, Mick Mulvaney, told the Associated Press on Thursday.

It’s not clear how Republican leaders can appease their president by funding the wall while avoiding a shutdown. And that impasse is a big reason budget experts say it’s 50-50 the government shuts down next week.

3. It’s uniting Democrats.

Democrats have their own divisions to deal with. But opposing Trump’s wall is a near-perfect rallying cry nearly everyone in their party can get behind. It’s just too good an opportunity to whack Trump and Republicans in Congress.

If Congress funds Trump’s wall, Democrats can argue Trump has broken yet another campaign promise by building a wall without getting Mexico to pay for it. (Trump says he eventually will force Mexico’s hand.) They can also argue Republicans are raising the deficit and that they’re teetering on a shutdown when they control Washington because of this wall.

Perhaps most importantly, Democrats have public opinion on their side.

While popular with his base, Trump’s wall has never been that popular with the United States. Fifty-four percent of Americans oppose building a wall along the entire Mexican border, according to CNN exit polling from the 2016 election. (Trump has said he’s willing to skip some parts.)

A recent KVUE Austin poll found that in Texas (Trump country), 61 percent oppose his wall.

4. It’s blocking Trump’s ability to get other things done.

Trump’s relationship with Congress right now isn’t great.

Democrats despise him. Republicans want to work with him, but his leverage with the party is questionable. (Witness Republicans’ inability a few weeks ago to pass a health-care bill despite Trump’s urging and growing evidence in places like Georgia that Trump’s political sway won’t make or break elections.)

Trump can’t afford to exacerbate tensions with either side of Congress if he wants to reform the tax code or restart health care, or – siren alert – avoid another government shutdown in October, when Congress has to pass a spending bill for 2018.

Ironically for the president, pushing his centerpiece campaign promise right now is undermining the rest of his agenda by pushing the very people he needs to pass laws away from him.