Updated at 11:35 a.m. ET
The House of Representatives voted Thursday 232-196 to pass a resolution formalizing its impeachment inquiry into President Trump.
Amid the debate, House Speaker Nancy Pelosi, D-Calif., called it a "sad day."
"It's a sad day because nobody comes to Congress to impeach a president of the United States. No one," she told reporters. "We come here to do the work, make the future better for our children, for America's future. We take an oath to protect and defend the Constitution, and that's what we cannot ignore and will not ignore when the president's behavior indicates that that investigation, that inquiry, is necessary."
House Democrats released a draft version of the resolution, which outlines the next steps of the inquiry, on Tuesday. The resolution authorizes the chairman of the House Intelligence Committee to conduct open hearings and allows the president and his attorneys to cross-examine witnesses.
The resolution also directs the House committees leading the inquiry to report their findings to the House Judiciary Committee, which will decide whether to recommend moving forward with articles of impeachment.In her press conference ahead of the vote, Pelosi also pushed back on Republican claims that the process is a "sham" and unfair to the president. The procedures in the resolution are "very transparent and open," she said, "giving more privileges to the president and his argument than were given in the past."
Immediately after the vote, President Trump tweeted, "The Greatest Witch Hunt In American History!"
Witnesses continue to testify behind closed doors in the inquiry. Thursday's witness, Trump's Russia director Tim Morrison, is set to leave the National Security Council, as NPR first reported.
On Wednesday, two State Department officials spoke with House investigators about their work on U.S.-Ukraine issues and the role of Trump's personal attorney Rudy Giuliani in Ukraine policy.Lawmakers also heard this week from Lt. Col. Alexander Vindman, who testified about repeatedly raising concerns to his superiors about Trump's demands that Ukraine investigate former Vice President Joe Biden and his son Hunter.
Vindman also told lawmakers that he feared Ukraine complying with the president's demands would lead to the loss of bipartisan support and would "undermine U.S. national security."