A former federal prosecutor says it could be the final nail in the coffin for Donald Trump if a new defendant charged in the Mar-a-Lago documents probe flips an outcome that she believes is very likely.

Prosecutors this week charged a third person , Mar-a-Lago maintenance worker Carlos De Oliveira, in the federal case involving classified material Trump took from the White House to his Florida estate.

De Oliveira is accused of helping Trump aide Walt Nauta, the other person previously charged with Trump in the case, move boxes of classified documents stashed at Mar-a-Lago, and then lying to federal investigators about it. He also allegedly followed Trumps orders to try and erase surveillance footage.

This is a defendant who has almost no choice but to flip, former U.S. Attorney Joyce Vance said in an analysis on MSNBC Thursday. Hes looking at spending a big chunk of time in prison if he goes forward.

Pointing to De Oliveiras interview with the FBI , Vance said De Oliveira lies to them in a bald-faced manner, so they have him dead to center if he does not cooperate.

Vance said De Oliveiras cooperation would be key in helping prosecutors prove Trumps criminal intent.

If he does cooperate, he is putting Trump front and center in this scheme to obstruct, she continued. They have Trump wanting to figure out if the videos can be erased. And this is so important in showing that this was not an innocuous effort by the former president to hold on to trophies or souvenirs from his time in office, but that he, in fact, knew that what he was doing was wrong.

And so, if they can obtain De Oliveiras cooperation, thats probably the final nail in the coffin on this one.

Trump was charged with three additional felonies in the probe, adding to the 37 he already faced, according to Thursdays superceding indictment. The new charges include additional counts of willful retention of documents and obstruction of justice, alleging the three defendants schemed to delete security camera footage at the Mar-a-Lago Club to prevent the footage from being provided to a federal grand jury.