President Donald Trump reacting after signing H.J. Res. 37, in the Roosevelt room of the White House in Washington, D.C., March 27, 2017. Reuters

President Donald Trump's initial campaign promise was a rather simple one: if elected, he would order the federal government to build a "big, beautiful" wall sprawling nearly 2,000 miles across the U.S.-Mexico border.

Now seated in the Oval Office, Trump has quickly realized garnering enough votes to support his political agenda in the House can be difficult. After failing to deliver on another of his campaign promises — repealing and replacing the Affordable Care Act — Trump could find himself facing a potential government shutdown if he isn't able to rally enough of Congress behind his border wall, projected to cost $20 billion.

Read: Trump's Wall Could Be A Big, Beautiful And Solar 'Technological Wonder' Along Border

Republicans were reportedly crafting a proposal that will tweak Trump's budget, leaving his border plans out of the federal funding bill for the next fiscal year. Congress has until April 28 to mark up and vote on the White House budget in order to avoid a government shutdown.

A general view showed a newly built section of the U.S.-Mexico border fence at Sunland Park, opposite the Mexican border city of Ciudad Juarez, Mexico Jan. 26, 2017. Reuters

"What I would like to see is a plan for how the money would be spent and a good faith discussion about what border security is really composed of," Senate Majority Whip John Cornyn, R-TX., said in a Politico interview published Tuesday. "We haven’t had that."

Recently leaked Department of Homeland Security documents revealed Trump’s administration had located just $20 million to begin the president’s southern border construction project – roughly $19,980,000,000 short of a total price tag Democrats warn American taxpayers will eventually be forced to pay.

Trump's wall faces a "big problem," House Minority Leader Chuck Schumer, D-NY., said in an interview with ABC’s George Stephanopoulos Sunday. "Republicans are opposing. Texas, Arizona, because there’s eminent domain and you have to take the private land."

Trump's chances of building a border wall decrease if he employs the same business strategy he used during last week’s health care debate, in which he demanded a vote by Friday regardless of how far along his party’s talks on the bill were, Schumer said.

"Instead of trying to jam it through on this short-term budget and say take it or leave it, we should debate it in 2018’s budget over the summer," Schumer said. "And, by the way, my prediction, it wouldn’t get the votes on either the Democratic or Republican side."