If House Democrats are unsure how to move forward post-impeachment, President Donald Trump's unhinged performances last week at the National Prayer Breakfast and in the East Room of the White House should provide some clarity. Trump unleashed a stream-of-consciousness tirade Thursday, using inflammatory words like "scum," "sleazebags" and "crooked" to describe his perceived enemies.

This was Trump uncensored and uninhibited, seemingly liberated from the confines of impeachment and determined to exact revenge on his public list of enemies. It was a demonstration of remarkable pettiness but also a warning that if he is left unchecked, there are few boundaries he won't cross to avenge his perceived slights.

This was Trump uncensored and uninhibited, seemingly liberated from the confines of impeachment and determined to exact revenge on his public list of enemies.

It's easy to understand why some Democrats may feel reluctant to resume vigorous oversight of Trump and his administration. Since the impeachment proceedings began last fall, congressional investigative committees have been running a marathon at a sprinter's pace. They are understandably tired, burned out and, given the actions of the Republican-controlled Senate, cynical. Will anything they do going forward make any difference? Some may be worried that resuming congressional investigations could affect the Democrats' efforts to defeat Trump in November.

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But clearly, many facts surrounding impeachment remain unclear. House Judiciary Committee Chairman Jerry Nadler, D-N.Y., has said the House "will likely" subpoena former national security adviser John Bolton for the testimony he refused to provide voluntarily during the impeachment inquiry. (The president's legal team has publicly said it would use executive privilege to block Bolton from testifying.) Secretary of State Mike Pompeo was subpoenaed by the House back in October, but he ignored the deadline to produce documents related to Trump's bullying tactics in Ukraine. Acting White House chief of staff Mick Mulvaney claimed that "absolute immunity" prevented him from complying with a subpoena the House issued in November.

But it's not just testimony and documents related to impeachment that warrant congressional scrutiny. New documents have exposed the "unprecedented — and largely hidden — business relationship" between Trump's businesses and the Secret Service. We still don't have an accurate understanding of the events that almost brought our country to the brink of war with Iran just one month ago. The Supreme Court is set to hear arguments on March 31 related to the House's efforts to subpoena Trump's tax returns.

Even though we know the president and his men will not comply with congressional subpoenas, they should still be issued. If they are ignored, those officials should be held in contempt. If they still refuse to acquiesce, they should be taken to court. As we've seen with the fight over Trump's tax returns, the judicial process takes time. It's unlikely any new cases will be resolved by the November election. But it's because these cases take time that House Democrats need to start right now.

Imagine a world in which Trump wins re-election. These efforts to fight for transparency and accountability will be the only thing we have left to preserve our democratic institutions. But we must start working through that process now, before it's too late to make much of a difference.

Republicans are almost certain to argue that if Democrats pursue vigorous oversight of the president, they'll be using their congressional power to re-litigate impeachment and unduly influence the 2020 elections. This is an exercise in false equivalency. Republicans used theHouse Select Committee on Benghazi to attack Democratic presidential front-runner Hillary Clinton, even issuing an oversight report in June 2016, mere months before Election Day.

Trump and his accomplices are betting that Democrats don't have the stomach to keep fighting. They think they can effectively send Democrats into retreat mode. If that were to happen, I fear, the damage done to our institutions will be even more grave — and it will certainly last longer. Post-impeachment, Trump has been the poster child for why our country needs an urgent check on his dictatorial impulses.

Doing his best "Saturday Night Massacre" impression Friday, Trump seemed to retaliate against two key witnesses from the House impeachment inquiry: recalling Gordon Sondland, the U.S. ambassador to the European Union, and removing Army Lt. Col. Alexander Vindman from his White House job (as well as Vindman's brother). There are reports that Trump is also thinking about punishing the intelligence community's inspector general, Michael Atkinson, for the great transgression of doing his job and transmitting a whistleblower's report to Congress.

As someone who worked at the House Oversight Committee, I understand the impulse to embrace a "do no harm" mentality as we head into election season. However, the American people delivered Democrats a sweeping mandate in the 2018 midterms to be a check on the Trump presidency.

These recent displays of power from Trump reveal a president who is doing literally whatever he wants. And he recognizes that Republicans in Congress are unable or unwilling to stop him. Therefore, the most meaningful thing House Democrats can do post-impeachment is to reignite their oversight fight and keep pushing to maintain vital checks and balances between the executive and legislative branches.