Trump-Ukraine scandal lights up Washington. Cue oversight debate.

President Donald Trump’s apparent pressure on the leader of Ukraine to investigate former Vice President Joe Biden and his son is only the latest norm-busting behavior from a United States chief executive who has long reveled in pushing past barriers that constrained his predecessors.

From revoking California’s ability to limit auto pollution, to attempting to add a citizenship question to the Census, to declaring a national emergency to build his border wall, President Trump has tried in numerous ways to take contentious actions he wants, sometimes against the advice of his own Cabinet members.

The legality of many of these actions remains to be seen. Lawsuits may clog the courts for years to come.

But if nothing else the Trump presidency has underscored the limits of the Constitution in regards to checks on presidential behavior. The Founding Fathers perhaps did not envision an Oval Office occupant such as him – and a Congress so riven by partisanship it cannot effectively restrain the executive branch of government.

“Formal constitutional checks are difficult. It’s always been difficult for Congress to wield the power it’s been given ... even before President Trump,” says Douglas Kriner, a professor in the department of government at Cornell University.

This is particularly true in the area of national security. Article 2 of the Constitution vests considerable authority in the president to say and do unpalatable things in the secret conduct of foreign relations. That is dangerous discretion, but has long been thought worth it on balance, noted Harvard Law professor Jack Goldsmith on Twitter last week.

“Trump has been challenging this principle, in various guises, for almost three years,” the conservative Professor Goldsmith tweeted following the Ukraine revelations. “He has shown time and again the extent to which our constitutional system assumes and relies on a president with a modicum of national fidelity, and decent judgment, and reasonableness.”

Ukraine, in context 

President Trump’s critics have long thought his interactions with foreign leaders have sometimes exhibited questionable judgment.

In May 2017, he infuriated U.S. and Israeli intelligence leaders by disclosing highly classified Israeli capabilities in a meeting with Russian Ambassador Sergey Kislyak. He also told Russian officials that firing “nut job” FBI Director James Comey took “great pressure” off him.

President Trump has taken steps to conceal his conversations with Russian leader Vladimir Putin by limiting the presence of other U.S. officials and, at one point, taking control of his interpreter’s notes.

“What I say to him is none of your business,” he told reporters in June.

This is some of the context for the current uproar over Mr. Biden and Ukraine.

What’s known is that the director of national intelligence, after consultation with the Department of Justice and apparently the White House, is withholding from Congress a whistleblower complaint made by someone within the intelligence community. News reports and Mr. Trump’s own statements have made clear that it involves in some manner a discussion between the U.S. president and Volodymyr Zelenskiy – who took office in May as Ukraine’s president – about Hunter Biden’s business interests in Ukraine when his father was vice president. 

Democrats say the administration is clearly violating the law by refusing to pass along a valid whistleblower allegation, as the statute in question requires. They also charge that the White House has improperly interfered with a valid inspector general investigation of the whistleblower’s charges. The whole point of having an official whistleblower process is to protect against such meddling, critics point out.

But under the Constitution’s Article 2 presidents have great power to conduct U.S. foreign policy in secret. The president is in charge of U.S. intelligence and classified information. Some legal experts say this could allow a legitimate basis for the White House to sit on the whistleblower’s complaint.

Any legal challenge in this instance would enter a “constitutional thicket” wrote legal expert and former FBI agent Asha Rangappa in The Washington Post on September 20.

Partisan roadblocks

The normal process of congressional oversight would be one way for House Democrats to respond in this instance to President Trump’s denial of information and allegations that he targeted a political rival using presidential powers. Committees could call administration witnesses and subpoena documents to try and determine the facts of the case.

But Democrats have been trying that for months, ever since the publication of Mueller Report, and it has not been working very well. The administration has stonewalled, withholding documents and instructing witnesses to remain mum. Court challenges promise to drag on for months, if not years.

“Oversight is a way for Congress to try and put political pressure on the White House by bringing things to light. And one of the big advantages [of that] is Congress can hold hearings with one swing of a chair’s gavel,” says Mr. Kriner, co-author of “Investigating the President: Congressional Checks on Presidential Power.”

But that check is totally dependent on Congress being able to get access to the information it needs. “What we’re seeing is a level of obstruction that’s really unprecedented,” says Mr. Kriner.

Democrats also charge that Republicans within Congress are abetting that obstruction. The Founding Fathers envisioned that the legislative branch and the executive branch would be natural rivals and compete for power. They did not count on partisanship so powerful that parties would be the rivals, dividing Congress and weakening its ability to respond to a unified executive.

“The theory of the system is designed, in this case, so that members of Congress would use their tools, which are many. But that depends on members of Congress setting aside partisan considerations . . . It’s not automatic. It requires people to do their jobs,” says Chris Edelson, assistant professor in the department of government at American University and author of “Power Without Constraint: The Post-9/11 Presidency and National Security.”

Unless a few key Republicans revolt against President Trump and bring the rest of the caucus with them, this situation won’t change. Thus the president has figured out that congressional enforcement mechanisms are mostly notional, says Paul Rosenzweig, a senior fellow in national security and cybersecurity at the public policy research firm R Street.

If the House begins a formal impeachment process, it would most likely expedite cases in the courts dealing with oversight access, says Mr. Rosenzweig. The question then would be: Would they actually take the vote to impeach President Trump?

If the process does not move along “the failure to act will inevitably result in the wholesale weakening of institutions and processes that undergird American democracy,” he says.