WASHINGTON (Nexstar) — As House Democrats move forward with their impeachment inquiry into President Trump, the power that Congress holds (or lack thereof) is on display.

“This is a scam by the democrats to try to win an election that they’re not going to win in 2020,” said President Donald Trump.

The White House is fighting back on every front—blocking witness testimony, ignoring subpoenas, and invoking executive privilege. So when the White House takes this approach, what real power do Congressional investigators have to force the White House to comply? What consequences are there for stonewalling the inquiry?

“So the assertion of the executive’s authority to disobey the will of a co-equal branch of congress has reached a level that we have never seen in this country’s history,” said George Washington University Law Professor Paul Schiff Berman. He says the showdown is a constitutional crisis

“Law is only as powerful as peoples’ willingness to follow it,” said Berman.

So, where does that leave Congress? Berman says it has two options, move ahead with articles of impeachment or take it to the courts.

“The problem with going to court is that it then delays the process,” said Berman. Some experts say that leaves House Democrats without a strong hand to play.

“Congress doesn’t have any really powerful tools at its disposal to quickly force the executive branch to hand over information,” said Gene Healy, with the Cato Institute.

From the beginning. House Republicans have said the inquiry is just another attack on the President. Democrats say the American public deserves transparency.

“He’s doing his job, his duty, as commander in chief, his duty as the President of the United States,” said Rep. Jim Jordan (R-Ohio).

“The American people have the right to know if the president is acting in their interests,” said Adam Schiff (D-California).

Berman says who will end up knowing what and when depends largely on the White House.