After special counsel Robert Mueller spoke publicly for the first time since he was appointed to lead the investigation into the Trump campaign’s alleged ties to the Russian government, the calls to impeach President Trump once again reverberated through the halls of Congress.

Before Mueller spoke, only six of the Democrats running for president in 2020 had demanded that Congress begin impeachment proceedings. After Mueller spoke, that number increased to 10 with Sen. Cory Booker of New Jersey, South Bend, Ind., Mayor Pete Buttigieg, Sen. Kirsten Gillibrand of New York, and former Colorado Gov. John Hickenlooper joining a Democratic chorus led by Sen. Elizabeth Warren of Massachusetts.