It will be nearly “impossible” for former Trump campaign chairman Paul Manafort to clear his name by simply smearing the defense’s top witness, according to former U.S. Attorney Joyce Vance.

Manafort, who is facing charges of bank and tax fraud charge, is expected to instruct his attorneys to attack the credibility of Rick Gates, a former employee who struck a deal to testify against Manafort. Gates admitted during testimony this week that he embezzled thousands of dollars from Manafort.

But Vance pointed out to MSNBC’s Andrea Mitchell on Tuesday that it will be all but impossible for Manafort to convince the jury that he is not guilty by attacking Gates’ credibility.

“The prosecution would… have to hit the ball completely out of the park to get an acquittal in this case,” Vance explained. “They’re using him in essence to give the jury access to Paul Manafort’s own words through his emails. This morning the prosecution had Gates discuss his email exchanges with Manafort where Manafort in essence directed the illegal activity he’s charged with.”

She added: “It will be difficult if not impossible for Manafort to lay this one off on Gates, even though the next thing the defense will have the chance to do is to thoroughly cross-examine Gates, so we’ll see how he holds up.”

NBC News reporter Ken Dilanian also remarked on “how badly this trial appears to be going for Paul Manafort.”

“There is a chance for the defense to make a case that Gates is lying,” Dilanian observed. “But there are these documents that seem to buttress what [Gates is] saying.”

Watch the video below from MSNBC.