A top Pentagon official as recently as last month vowed the department would not tolerate "any act of retaliation" against Lt. Col. Alexander Vindman -- a pledge now being put to the test after Republican Sen. Marsha Blackburn this week repeatedly attacked the key National Security Council aide who testified before Congress on the Ukraine scandal.

CNN chief legal analyst Jeffrey Toobin says White House counsel Pat Cipollone's claim that the Trump administration will not cooperate in the Senate impeachment trial at all is concerning.

President Donald Trump was impeached in December by the Democratic-controlled House of Representatives, but now it's up to the Republican-led Senate to decide whether to remove him from office.

Nine days from the Iowa caucuses, Democratic presidential candidates are fighting bad winter weather and the headwinds of an impeachment trial that's dominating national headlines and latching the senators in the race to Washington instead of the campaign trail.

In the legal and political arena, you always want the last word. That theory held true in the 1999 impeachment of President Bill Clinton. The House managers led by Henry Hyde and the likes of Lindsey Graham made an impressive case over three days. But Clinton's brilliant White House counsel blew away those three days of arguments in a presentation that destroyed the foundation of the House managers' case. While the trial dragged on for several weeks, Charles Ruff, Clinton's counsel, had the last word long before the trial ever ended.

CNN's Manu Raju reports that Sen. Susan Collins (R-ME) shook her head and disagreed when Rep. Adam Schiff (D-CA) cited a report by CBS that President Trump was pressuring GOP senators about their impeachment votes.

Former federal prosecutor Anne Milgram takes impeachment questions as Democrats wrap up their case against President Donald Trump. Watch "Full Circle" live weeknights at 6:30 p.m. ET.

As Democrats end their opening arguments, House manager Adam Schiff (D-CA) predicts what President Trump's attorneys will argue during the impeachment trial.

After months of anticipation, legal auditions on cable news and daily preparatory sessions inside West Wing conference rooms, President Donald Trump will get his proverbial day in court this weekend -- though he's not sure anyone will be watching.