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President Donald Trump's Senate impeachment trial began in earnest Tuesday, with prosecutors from the House of Representatives and attorneys for the White House tangling over how the case should proceed.

Nearly all votes on changes to the trial format showed Democrats and Republicans split along party lines, but the last-second handwritten changes gave Democrats hope that some Republican senators will consider their requests for documents and witnesses later on.

Here are six key things that have happened during Tuesday's trial proceedings.

Democrats fail to change McConnell's rules

As expected, Minority Leader Chuck Schumer, D-N.Y., offered several amendments to Majority Leader Mitch McConnell's organizing resolution — essentially a blueprint for how the third presidential impeachment trial in U.S. history will proceed.

The first, which would allow the Senate to subpoena White House records, was defeated along party lines, 53-47. A second, to subpoena State Department documents related to the charges against the president, was also defeated along party lines, 53-47. Schumer immediately proposed a third amendment, to subpoena documents from the White House Office of Management and Budget, which also failed.

Undeterred, Schumer proposed a fourth amendment, to subpoena acting White House chief of staff Mick Mulvaney, a key figure in events like the unusual freeze on millions of dollars in military aid to Ukraine, which prompted House Democrats to launch an impeachment inquiry. Again, the amendment failed, 53-47.

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A seemingly exasperated McConnell, R-Ky., asked Schumer whether he was willing to "stack" his remaining amendments, a procedure to speed voting. Schumer refused.

"We believe witnesses and documents are extremely important and a compelling case has been made for them," he said. "We will have votes on all of those."

Schumer agreed to postpone the rest of his amendments until Wednesday, but after a brief negotiation, he introduced a fifth amendment, to subpoena certain Defense Department documents and records. It, too, was defeated, 53-47.

Schumer introduced his sixth amendment, sending the first day of the impeachment trial late into the night. He moved to subpoena the testimony of Robert Blair, a senior adviser to Mulvaney, and Michael Duffey, the associate director of national security at the Office of Management and Budget, who oversees the process for approving and releasing U.S. assistance to foreign countries. And like the five before it, the amendment was tabled on a vote of 53-47.

The Democrats' seventh amendment of the day would require that if either party seeks to admit evidence that has not been submitted as part of the House record and that was subject to a duly authorized subpoena, that party shall provide the opposing party with all other documents responsive to the subpoena.

The amendment suffered the same fate as the previous six, and Schumer introduced an eighth amendment, calling for former national security adviser John Bolton to testify. That amendment, as well as a ninth that would have forced the Senate to vote on each potential motion to subpoena witnesses or documents, was tabled on the same 53-47 party-line vote.

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A 10th amendment, to require adequate time for all parties to respond to motions, elicited the first Republican defection, Susan Collins of Maine. It was tabled, 52-48.

A final 11th Hail Mary amendment sought to put the power to determine whether witnesses should testify in the hands of the judge, Chief Justice John Roberts. The final amendment was tabled, 53-47, at 1:40 a.m. ET.

With the Democrats' lineup of amendments exhausted, the Senate passed McConnell's organizing resolution laying out the rules for the rest of the trial, which includes delaying debate over any witnesses until after both sides have made their arguments.

Fireworks and Roberts' scolding

Debate over the Democrats' attempt to force a subpoena of Bolton got heated as House manager Jerry Nadler, D-N.Y., and Trump counsel Pat Cipollone traded personal attacks, prompting Roberts to issue a stern warning.

The temperature in the Senate rose when Nadler tried to lay the pressure on the backs of the 100 senators.

"The president is on trial in the Senate, but the Senate is on trial in the eyes of the American people," Nadler said. "Will you vote to allow all the relevant evidence to be presented here? Or will you betray your pledge to be an impartial juror?"

Cipollone shot back that Nadler was accusing senators of a cover-up. "Mr. Nadler, you owe an apology to the president of the United States and his family. You owe an apology to the Senate, but most of all, you owe an apology to the American people," he said.

The exchange prompted Roberts to interrupt with a warning.

"I think it is appropriate at this point for me to admonish both the House managers and the president's counsel in equal terms to remember that they are addressing the world's greatest deliberative body," Roberts said. "One reason it has earned that title is because its members avoid speaking in a manner and using language that is not conducive to civil discourse.

"I do think those addressing the Senate should remember where they are," Roberts added.

A preview of coming attractions

The House managers and attorneys for the White House used their time debating Schumer's amendments to give sneak previews of their opening arguments.

House managers repeatedly referred to evidence they collected from Trump administration officials about the withholding of millions of dollars in military aid to Ukraine, underscoring the White House's refusal to hand over any documents related to the freeze while blocking key witnesses from testifying.

The unusual aid freeze, prosecutors argued, was part of a larger pressure campaign directed by Trump to get Ukrainian President Volodymyr Zelenskiy to announce investigations that would benefit the president personally and politically.

White House attorneys contended that the president didn't do anything wrong and argued that their client was denied due process in the House investigation.

The writing is on the resolution

Two items that had caused a stir in McConnell's resolution apparently were changed shortly before the document was read into the record Tuesday.

A provision that would have given both the House managers and attorneys for the White House just two days to deliver their allotted 24 hours of opening statements was changed to give them three days each. McConnell also tweaked another provision criticized by Democrats that would have barred automatically entering all of the evidence House Democrats gathered into the Senate record.

The changes were written by hand on the resolution, with other lines crossed out.

Clinton's precedent looms

A spokeswoman for Sen. Susan Collins, a moderate Republican from Maine, said the changes to the resolution were made after she and other Republicans complained that the rules strayed too far from the ones used in the President Bill Clinton's Senate trial in 1999.

Trump reacts

Trump was in Davos, Switzerland, for the World Economic Forum, but he weighed in on Twitter with a single demand.

"READ THE TRANSCRIPTS!" he tweeted, possibly referring to the White House record of his call with Zelenskiy in July (the document notes that it is not an exact transcript).

During the call, Trump asked Zelenskiy to investigate former Vice President Joe Biden, a possible general election rival, and his son, Hunter Biden, as well as a conspiracy theory related to the 2016 election. Read the full record here.