There is little doubt about the outcome: both articles of impeachment will advance to the House floor on a party-line vote. But Democrats opted for a daytime final vote following a lengthy debate over Republican-authored amendments. The move stunned Republicans, who said they were ambushed by the decision and viewed it as a sign of disrespect.

When the committee does approve the articles on Friday, it will mark just the fourth time in history the impeachment process has advanced this far.

The committee began formally debating the articles late Wednesday night, with lawmakers making direct appeals to their colleagues across the aisle. The debate continued late into the night on Thursday as Republicans offered several amendments to chip away at the articles of impeachment; all were doomed to fail on party-line votes.

Inside the cavernous Capitol Hill hearing room, Democrats made clear that they intended to indulge the string of GOP amendments as long as Republicans were willing to debate them. Though many members of the public flooded the hearing room when the session began early Thursday morning, the audience had mostly cleared out by 9 p.m. — even as the proceedings showed no signs of winding down.

Unsurprisingly, both sides remain entrenched, and lawmakers grew increasingly agitated as Thursday’s session entered its thirteenth hour. Some lawmakers even became visibly drowsy as their colleagues launched into repetitive and often passionate diatribes — with little indication that either party was prepared to concede on even a single point of debate.

Republican leaders have been working intensely to ensure that none of their rank-and-file colleagues join Democrats in favor of impeachment, and so far they are confident they have succeeded.

Republicans used their time during Thursday's hearing to offer amendments to strike various aspects of Democrats’ articles of impeachment and accuse the majority of procedural violations.

An amendment offered by Rep. Jim Jordan (R-Ohio), for example, would have eliminated the “abuse of power" article, while another one, offered by Rep. Matt Gaetz (R-Fla.), would have added language about former Vice President Joe Biden’s son, Hunter, to the articles. The GOP amendments were defeated on party-line votes.

The committee’s debate over articles of impeachment was fairly orderly and even substantive at times, focusing on what constitutes an impeachable offense and whether the evidence Democrats presented meets that standard. Republicans argued — as they have throughout the investigation — that Democrats’ case falls far short of warranting impeachment, while Democrats described it as open-and-shut.

A nearly three-month investigation by the House Intelligence Committee produced a 300-page Democrat-authored report alleging that Trump abused his power by pressing Ukraine to investigate his political rivals. The report also describes an alleged effort by Trump to withhold critical military aid and a coveted White House meeting in order to further pressure Ukrainian President Volodymyr Zelensky to announce investigations, including one targeting the Bidens.

Trump has mounted an unprecedented effort to resist Democrats’ inquiries, ordering all White House officials to defy document and testimony requests — even subpoenas — ensuring that lawmakers were unable to question several senior Trump administration officials.