U.S. President Donald Trump has shifted his focus to tax reform, but investors should not expect an easy or quick passage for that key piece of his economic agenda.

Following the first-round failure to repeal Obamacare, Steven Billet, a professor at George Washington University, told BNN in an interview it has become quite clear that the Trump Administration does not know how to work with Congress.

“It’s amateur hour at the White House,” the director of the master’s in legislative affairs program at GWU said. “It was a massive failure with health care reform.”

Billet knows the inside track in Washington, having worked in the congressional offices of former Maryland Senator Barbara Mikulski and John Brademas, former Majority Whip in the U.S. House of Representatives for the Democratic party. 

“They don’t have a very good legislative operation,” said Billet. “It’s apparent the president can’t tweet his way to (getting) any piece of major legislation” passed.

The last major overhaul of the U.S. tax system occurred in the mid-1980s. According to Billet, it was a “brutal process” and it will be no different this time. 

“This will take a long time,” he said.  “It will involve major committees in both the House and Senate, and a section-by-section reconsideration of the entirety of the tax code.”

“It [reforming the tax code] will not be one of those issues where the president can intervene and push the Congress in a particular direction.”

Billet said there’s only a 50-50 chance of tax reform being passed before the end of this year.