We also know that senior members of the Trump campaign, including the president’s son, son-in-law and campaign chairman, met with Russians who promised “dirt” on Mrs. Clinton. If there was in fact “no collusion,” as the president so often claims, it apparently was not for lack of trying. The special counsel has secured guilty pleas on serious federal felony charges from Trump associates, including Mr. Trump’s campaign chairman, Paul Manafort; the deputy campaign chairman, Rick Gates; a former national security adviser, Michael Flynn; a Trump campaign foreign policy adviser, George Papadopoulos; and Mr. Trump’s former personal lawyer, Michael Cohen.

What do all these men have in common? They lied to investigators about the nature of their relationships with foreign powers, and they worked for the Trump campaign. And that’s before we even start talking about Roger Stone.

Regardless of whether efforts by Trump associates to coordinate with or benefit from interference by Russia or WikiLeaks were criminal, the fact that Mr. Trump and his campaign strategists sought to benefit from a foreign adversary’s efforts to undermine our democracy is one of the greatest breaches of public trust our country has ever witnessed. If Mr. Mueller ultimately determined that indicting the president’s associates for this conduct was not appropriate, that does not mean that there should not be consequences for this outrageous breach of trust.

Though these and other findings have already been made public, many key questions remain. Chief among these is whether the special counsel found evidence that Mr. Trump obstructed justice by engaging in a pattern of conduct calculated to impede investigations of his campaign and his administration, including by firing Mr. Comey; attempting to force out the previous attorney general, Jeff Sessions, and pushing Mr. Sessions to reverse his recusal from the Russia inquiry; and potentially by dangling pardons to key defendants. Congress and the American people deserve to know the truth about the facts and circumstances of the president’s possibly obstructive acts. Obstruction of an investigation is not only criminal conduct, but also an affront to our system of government and the faith that the American people have in it.