The Washington Post reported last week that “President Trump’s allies are waging an increasingly aggressive campaign to undercut the Russia investigation by exposing the role of a top-secret FBI source. The effort reached new heights Thursday as Trump alleged that an informant had improperly spied on his 2016 campaign and predicted that the ensuing scandal would be ‘bigger than Watergate!’”

That was a convoluted, and hyper-cautious, way of explaining the obvious: President Trump is actively engaged in a campaign to undercut special counsel Robert Mueller’s inquiry into misdeeds associated with the Trump campaign and, presumably, the Trump presidency.

Trump was right in one respect; the level of presidential wrongdoing we are now witnessing is, in fact, “bigger than Watergate.” And it is remarkable the extent to which this wrongdoing is playing out in real time, often on Twitter. Trump has taken to social media to demand a Department of Justice inquiry into allegations regarding the Federal Bureau of Investigation’a gathering information about Russian involvement with his campaign. The allegation that the FBI had an informant with expertise on the Russia issue is, Trump claims, the “biggest political scandal” of all time.

The president is wrong. The scandal here is not that the FBI scrutinized a campaign that engaged in activities that clearly demand investigation by law-enforcement agencies. The scandal lies in those activities in the first place. As Congressman Adam Schiff, the California Democrat who is the ranking member of his party on the House Intelligence Committee, says, “it would have been negligent for the FBI not to take steps to protect the country in the midst of information it was receiving.”

But there is not just one scandal. The second scandal, which has been unfolding for more than a year, involves an attempt by the president of the United States to undercut an ongoing examination of foreign influence on US elections, including the possibility that this president assembled an administration to meet the demands of those foreign influencers.

There is a lot that we do not know at this point. But there is an expectation that the ongoing investigation by Mueller and his team will provide answers to some of the most important questions.

There is mounting evidence—much of it provided by Trump on Twitter and in public statements—to suggest that the president is conspiring with congressional allies to use the corrupted power of the executive and legislative branches of the federal government to, as the Post so delicately suggests, “undercut” the investigative work in which Mueller and others are engaged.

What is missing at this point is a clear statement of what the consequence for the president must be if he impedes an investigation into wrongdoing by himself or those working on his behalf.

That consequence is impeachment. The founders of the American experiment established the impeachment power with moments such as this one in mind. At the Constitutional Convention of 1787, clauses discussing impeachment were framed around an understanding, expressed by George Mason, that “no point is of more importance than that the right of impeachment should be continued” for the president, the vice president and other top officials.

Why? Because the impeachment power provided an eternal answer to a pair of essential questions for a republic that had only recently thrown off the chains of monarchy: “Shall any man be above justice? Above all shall that man be above it, who can commit the most extensive injustice?”

It is hard to imagine a higher crime than presidential intervention to thwart an inquiry into presidential wrongdoing.

A few honorable members of Congress, such as Congressman Steve Cohen, the Tennessee Democrat who serves as the ranking member of his party on the House Judiciary Subcommittee on the Constitution and Civil Justice, have stated that impeachment must be on the table. Pointing to “evidence that he attempted to obstruct an investigation into Russia’s interference with the US presidential election and links between between Russia and the Trump campaign,” Cohen says: “The time has come to make clear to the American people and to this President that his train of injuries to our Constitution must be brought to an end through impeachment.”

But Cohen and brave members such as Adriano Espaillat of New York and Al Green of Texas are the outliers in a House Democratic Caucus that, for the most part, avoids serious discussion of presidential accountability.

Top Democrats have largely refused to embrace an essential truth of the American experiment: that the threat of impeachment is a necessary tool for maintaining a functional system of checks and balances. It is an unfortunate fact that the Republicans who currently form a majority in the House—the chamber that is charged with beginning an impeachment inquiry—are unlikely to respect their oaths of office. It may even be the case that some of those dishonorable members are conspiring with the president to undercut the inquiry.

But that is no excuse for dialing down discussion of impeachment. If there is any point to a two-party system, it is this: When one party is acting in a lawless manner, the other must be all the more vocal in explaining and defending the rule of law.

It is staggeringly shortsighted for Democratic leaders in the House to suggest that members ought not discuss impeachment because they imagine that doing so might help to rally supporters of Trump in the mid-term elections. For some prominent Democrats, this is a ruse to obscure their cowardice. For others, this is evidence that they really are as politically inept as their critics suggest—since only a fool would imagine that, if Democrats do not mention the “i” word, then Trump will refrain from doing so. No matter what Democrats say,Trump and his ruthless political strategists will mount a fall campaign that claims a Democratic takeover of the House will initiate an impeachment inquiry.

The problem at this point is not merely what Trump will do. The problem is also what House Democratic leaders are not doing. They are not making it clear that an impeachment inquiry is always valid when there is evidence of presidential wrongdoing, evidence of cover-ups of that wrongdoing, and evidence of efforts to undercut investigations into that wrongdoing.

Openly discussing the impeachment power, and clearly stating when and how it must be applied, puts the president on notice. It tells Trump that he must not thwart investigations into his campaign and his presidency because he is not above justice.

Impeachment isn’t the political “third rail” that cowardly Democratic “leaders” imagine.

Impeachment is the bottom line for a constitutional republic that demands accountability and respect for the law from all officials—but especially from presidents.