What the Manafort Verdict Means

The conviction conclusively and publicly demonstrates what many of us have said since the start of the investigation: This is no "witch hunt." It instead is one of the most successful special counsel investigations in history. Coming alongside the guilty plea by Michael Cohen, the president's former lawyer, implicating the president in campaign finance violations, it was a very bad day for Mr. Trump.

Mr. Manafort's conviction cannot be diminished by arguing, as Mr. Trump and his coterie are fond of doing, that the misconduct was unrelated to the Trump campaign or Russian "collusion." On the contrary, the trial evidence included Mr. Manafort's close ties to pro-Russia forces and his desperate financial straits as he "volunteered" his time for the next president. The trial revealed how willing Mr. Manafort was to corruptly leverage his position of influence over Mr. Trump during the campaign for his own personal benefit. He offered briefings to a pro-Russia Ukrainian oligarch and dangled a position in the Trump administration in front of a banker who provided him a loan for which he would not otherwise have qualified.

The conviction conclusively and publicly demonstrates what many of us have said since the start of the investigation: This is no "witch hunt."

The conviction also shows the caliber of the foe that President Trump is facing as he decides whether or not to sit for an interview with Mr. Mueller focusing on obstruction of justice. While we had already believed that Mr. Trump was unlikely to voluntarily sit for an interview, Tuesday's verdict makes that interview even less probable. We should now prepare for a potential extended legal battle about the scope and power of a possible Mueller-issued subpoena for the president's testimony.

It is unknown whether Mr. Mueller will go that route. If he does, however, his win in the Manafort case sends Mr. Trump the message that the special counsel and his team have the will and the ability to win a battle over a subpoena. Like in the Manafort case, the law is on their side. In United States v. Nixon, the Supreme Court unanimously held that a president cannot use executive privilege to withhold tape recordings of his words. There is no reason that the same principle should not also apply to their live utterance.

Mr. Manafort's conviction should also send chills down the spines of other potential defendants, possibly including the president's son Donald Trump Jr. and his informal adviser Roger Stone. As far as we know, they have been excluded from the hundreds of witnesses the special counsel has interviewed. That fact, and the public evidence about their conduct, signals that they may be facing Mr. Mueller's scrutiny.

They would be wise to study the Manafort trial as a preview of the prosecutions that could emerge next. As the legal pressure builds on these major figures, there could well be a corresponding increase in their desire to cooperate with the investigation. This pressure has already paid dividends to Mr. Mueller's investigation: Mr. Cohen entered a plea agreement on Tuesday afternoon on charges related to campaign-finance violations and bank and tax fraud. He had previously suggested publicly that he had information to share, and in court on Tuesday he implicated the president by indicating that Candidate Trump instructed him to make illegal payments to influence the election.

Notably, Mr. Cohen's plea agreement does not provide him with any protection from additional charges that could be brought by the special counsel. Mr. Manafort's conviction (together with mounting pressure on him from the Department of Justice investigation of his own alleged misdeeds) will only increase the pressure on Mr. Cohen to cooperate with Mr. Mueller's investigation to reduce his sentence.