Former US Ambassador to Ukraine Marie "Masha" Yovanovitch -- a highly respected career diplomat who unwittingly became one of the central figures in the impeachment drama -- has retired from the State Department.

The Senate voted down a motion to compel witnesses and documents at the impeachment trial. The final vote was 49-51 to defeat the motion. Republicans Susan Collins and Mitt Romney voted with the senators who caucus with the Democrats in support of the motion.

The Iowa caucuses are almost here. Voters will have a chance to express their preferences among the Democratic presidential candidates on Monday after months of campaigning, advertisements and televised town halls and debates. While Iowa alone will not determine the party's nominee, it will mark the official start of the campaign season.

As senators decided Thursday whether to call witnesses in Donald Trump's impeachment trial, the President did what he usually does: say numerous things that aren't true.

No Congress watcher expected Florida Sen. Marco Rubio to break with his party and vote either for witnesses to be called in the Senate impeachment trial or to remove President Donald Trump.

The Trump impeachment trial has been gripped by drama surrounding witnesses, particularly former national security adviser John Bolton: Will he or won't he testify?

Former Republican Ohio Governor John Kasich reacts to Sen. Lamar Alexander (R-TN) saying that he will oppose calling witnesses for the impeachment trial against President Donald Trump.

READ the senator's statement | 'Rushed and flawed': Murkowski criticizes the impeachment articles

The end appears on the horizon for the third impeachment trial of a president in US history, with the Senate poised to defeat a motion on Friday to seek witnesses and documents in the trial of President Donald Trump.

Republican hopes of blocking former national security adviser John Bolton's impeachment testimony highlight the Trump-era GOP's defining characteristic: its refusal to defy the President under almost any circumstances.