WASHINGTON, D.C. - If the U.S. House of Representatives approves Articles of Impeachment and votes to impeach President Donald Trump, a formal trial will be held in the U.S. Senate. There, senators will hear evidence from both Congressional Democrats and the White House among others. Without holding the title, senators essentially will become “jurors” in the trial.

Many Senate Democrats have been highly critical of President Donald Trump throughout the impeachment inquiry. But even some of the President’s biggest critics in the would-be jury and the case at hand, in which Democrats are accusing Trump of withholding U.S. military aid from Ukraine until the European nation investigated the president’s political rivals, are not yet calling for the President to be impeached. Sen. Mazie Hirono (D-Hawaii) is among those critics, and is so far only condemning the president’s actions.

“You can’t have a president running around doing this. This is not normal,” Hirono said. “This endangers our national security.”

If the quid pro quo does exist as some House Democrats claim, Sen. Kirsten Gillibrand (D-N.Y.) believes that would be criminal activity. However, like a true juror, Gillibrand said Tuesday she is waiting for evidence to be presented from both sides.

“My job isn’t to make a decision today,” Gillibrand said Tuesday. “My job is to wait until the House finishes their job and decides whether or not there is enough evidence to impeach.”

But the trial also becomes a numbers game.

A two-thirds majority – 67 out of 100 senators – is needed to convict Trump of the charges against him. Americans could learn more about those charges by the end of the year. The House Judiciary Committee will hold its first impeachment hearing on Dec. 4, Chairman Jerrold Nadler (D-N.J.) announced Tuesday.

But one look at the numbers show Republicans with a clear advantage to avoid convicting Trump. The partisan breakdown in the Senate: 53 Republicans, 45 Democrats, and two independents (Sen. Bernie Sanders of Vermont and Sen. Angus King of Maine) who both caucus with the Democrats. That means at least twenty GOP senators would have to side with Democrats, and a conviction right now is highly unlikely.

“It’s been a terrible process,” said Sen. Pat Toomey (R-Pa.), who has been critical of Trump on trade policy, but has also railed against the impeachment process.

So far, he said he hasn’t seen evidence of an impeachable offense necessary to remove Trump from office. Like Gillibrand, Toomey is waiting to see what the Articles of Impeachment may be.

“My attitude is I’m going to wait to see what they produce,” Toomey said. “If they do, they will send it over to the Senate and we’ll have plenty of work to do on our side.”

If a trial happens, it is likely to start in January and would run six days a week.

This would be just the third impeachment trial in U.S. Senate history, following trials for presidents Andrew Johnson and Bill Clinton.