The official moves came four weeks after the House had voted to impeach the President on two charges, as Democrats delayed in hopes of forcing Senate Republicans to call witnesses who refused to testify in House impeachment hearings.
While that gambit did not work, new evidence did surface over that time period, including documents and messages gathered by Lev Parnas, an indicted associate of the President's personal lawyer Rudy Giuliani.
Parnas worked with Giuliani in Ukraine, helping in his effort to force out then-U.S. Ambassador Marie Yovanovitch.
The new materials, which included texts and other electronic messages involving Parnas, Giuliani, and others, also held notes which mentioned getting Ukraine to announce "that the Biden case will be investigated."
It was the President's withholding of military aid - combined with an effort to ask for the Ukraine government to announce investigations of the Bidens and the 2016 elections - which prompted Democrats to convene impeachment hearings.
Republicans greeted the official arrival of the impeachment charges with scorn and ridicule.
"Democrats have politicized impeachment and denied President Trump his fundamental right to due process," said Sen. David Perdue (R-GA). "It’s clear Democrats in the U.S. House of Representatives failed to make their case."
"By delaying the process, Speaker Pelosi confirmed that this impeachment is a partisan political exercise," said Sen. Shelley Moore Capito (R-WV).