The breaking down of Paul Manafort’s plea deal has dealt a blow to special counsel Robert Mueller’s investigation. A witness to the June 2016 Trump Tower meeting between Jared Kushner, Donald Trump Jr., and a Russian lawyer predicated on damaging information about then-Democratic presidential nominee Hillary Clinton, Manafort was seen as a valuable potential witness in Mueller’s investigation into possible collusion between the Trump campaign and Moscow. The decision to call him out as a liar effectively takes his testimony off the table, removing a valuable asset for the government. It comes after a lengthy trial where prosecutors won guilty...