There’s a certain rhythm to the last two presidential scandals that led to impeachment proceedings. Richard Nixon denied that he had tried to cover up the Watergate break-in during the two-year scandal that followed. The Supreme Court forced him to hand over the White House tapes to prosecutors, including one in which he conspired to pressure the FBI to drop its investigation. He resigned rather than face near-certain impeachment in the House and removal in the Senate.

More than two decades later, Bill Clinton denied that he had a sexual relationship with White House intern Monica Lewinsky, both in public statements and in sworn testimony during the Paula Jones sexual-harassment lawsuit. Independent counsel Ken Starr found incontrovertible proof he had lied: a blue dress owned by Lewinsky with a stain from which Clinton’s DNA could be extracted. The House impeached Clinton for perjury and obstruction of justice, though the Senate later voted to acquit him.

Some House Democrats seem to hope that rhythm—fervent denials of wrongdoing, followed by a smoking gun that proves them wrong, followed next by some kind of action—will magically repeat itself for Donald Trump. Trump, however, has broken that cycle. The president fervently denies he’s done anything wrong, then cheerfully admits to most of what his critics allege. He constantly resists efforts to scrutinize and check his administration while carrying out some of the most overt acts of corruption in the public eye. Some two-and-a-half years into this routine, Democrats are still falling into the trap, waiting for a deus ex machina that never arrives. Others, including Speaker Nancy Pelosi, appear to be exploiting the lack of a Trump-slaying MacGuffin to justify their inaction.

What we know so far about the president’s latest scandal is troubling, to say the least. Rudy Giuliani, Trump’s legal hatchet man, is openly trying to dig up dirt on one of Joe Biden’s sons in Ukraine to damage the Democratic frontrunner’s presidential bid. Opposition research is hardly new to American politics, but Trump’s approach to it crosses multiple lines. The Wall Street Journal reported over the weekend that Trump repeatedly pressured Ukrainian President Volodymyr Zelensky in phone calls this summer to investigate Biden’s son and work alongside Giuliani to undermine Trump’s potential 2020 opponent.

An unidentified whistleblower filed a complaint with the U.S. intelligence community’s inspector general that partially covers some of these matters. Precise details about that complaint are elusive, even to members of the congressional intelligence committees. We know that the inspector general found the complaint to be serious enough to alert Congress about the standoff, notifying lawmakers that the complaint “relates to one of the most significant and important of the [director of national intelligence]’s responsibilities to the American people.” We also know that Joseph Maguire, the acting director of national intelligence, is resisting disclosures to lawmakers on the matter at the behest of the Justice Department.