Two new factors appear to stymie the impact of a potential Trump pardon for Manafort.

The first is that Manafort is already talking. One obvious rationale for a pardon would be to reward Manafort for holding out against Mueller’s pressure for cooperation in building a case against the president or those close to him. But Manafort’s lead lawyer said Friday his client has already cooperated with Mueller’s team, and Friday’s plea agreement says that Manafort "shall cooperate fully, truthfully, completely and forthrightly with the Government and other law enforcement authorities identified by the Government in any and all matters to which the Government deems the cooperation relevant.”

Even if Trump might have hoped to stop Manafort from singing, Friday’s plea suggests he has already reached the first chorus.

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Second, Mueller managed to get concessions from Manafort that limit the value of any pardon. Manafort admitted guilt on virtually all of the charges he faced in both Washington, D.C., and Virginia, including a slew of bank fraud charges. Each of those admissions could give state or local prosecutors a potential charge against Manafort that would survive even in the event of a Trump pardon, since he can pardon only federal offenses.

"By admitting to all of the facts in both indictments, the conviction is pardon proof in the sense that if Trump ever pardoned Manafort, a state attorney general could take Manafort’s admissions in the plea and use them to indict Manafort for state charges," former Watergate prosecutor Nick Akerman said.

The steps Mueller's lawyers have taken mean a pardon won’t likely be a particularly effective way of discouraging Manafort from offering Mueller whatever Manafort has that might be incriminating toward Trump, Trump Jr., Kushner or others.

However, if Trump wants to pardon out of mercy or spite, he will still have the power to do so. Such a move could immediately trigger Manafort’s release from jail and relieve him of the duty to turn over tens of millions of dollars in property and bank accounts to the government. State authorities may catch up with Manafort, but precisely how that will play out is uncertain.