Senate Majority Leader Mitch McConnell on Monday said the Senate would have “no choice” but to move forward with impeachment proceedings if the House ultimately votes to bring charges against President Donald Trump.

“I would have no choice but to take it up,” McConnell said in a CNBC interview. “How long you are on it is a different matter, but I would have no choice but to take it up based on a Senate rule on impeachment.”

Prior to this interview, there were some questions about how McConnell would handle impeachment charges. Although the Constitution designates the Senate as the body in charge of a potential trial, it does not require the upper chamber to actually follow through with such action. And given McConnell’s track record on congressional norms — in particular his decision to hold up Merrick Garland’s Supreme Court nomination — there was speculation that he might use the constitutional wiggle room to avoid addressing any articles of impeachment.

As McConnell noted, however, the Senate rules themselves are a bit more specific. And in the case of impeachment, McConnell is somewhat bound by them.

“It’s a Senate rule related to impeachment that would take 67 votes to change,” he added.

As McConnell alluded to Monday, Senate Republicans could make impeachment proceedings as perfunctory as they’d like, but if the House sends them charges, they’ll at least have to do something with it.

The Senate rules on impeachment, briefly explained

The Constitution offers some leeway on how an impeachment trial could be handled but Senate rules lay it out in more detail.

Under existing Senate rules, the upper chamber “shall” begin the process of considering articles of impeachment if charges are officially brought by the House:

Upon such articles being presented to the Senate, 102 the Senate shall, at 1 o’clock afternoon of the day (Sunday excepted) following such presentation, or sooner if ordered by the Senate, proceed to the consideration of such articles and shall continue in session from day to day (Sundays excepted) after the trial shall commence (unless otherwise ordered by the Senate) until final judgment shall be rendered, and so much longer as may, in its judgment, be needful.

According to Matt Glassman, a senior fellow at Georgetown University’s Government Affairs Institute, the Senate is fairly wedded to these rules, though it could always change how they’re interpreted if it had enough votes from its membership. A reinterpretation could involve a senator overseeing the rules deciding that they could be followed a different way, even if they remain in place. Such efforts would require both a recorded vote and a simple majority of senators to agree to them, notes the Niskanen Center’s Keith Whittington.

A wholesale revision of these rules, however, would require the support of 67 senators, as McConnell pointed out.

One-liner: The Constitution does not require a trial. Current Senate rules do require a trial. The Senate could unanimously ignore those rules. A majority could change those rules or otherwise dispose of the trial. A change/disposal would require at least one recorded vote.

— Matt Glassman (@MattGlassman312) September 29, 2019

“All the standing rules of the Senate require 67 votes to formally change,” Glassman tells Vox. “However, the Senate can ‘reinterpret’ those rules and set new precedents via a majority vote — by appealing decisions of the chair and having the Senate vote as a majority to alter the interpretation.”

Although Senate Republicans would theory have the numbers needed to push through a possible reinterpretation of the impeachment rules, a move like this could be risky, especially for lawmakers hailing from swing states.

Instead, a safer bet might be for Republicans to go forward with an impeachment trial and ultimately vote to acquit, a way to demonstrate their commitment to historic precedent while achieving the same result. Republicans could also use other procedural maneuvers to prevent the completion of a trial, even if the impeachment charges are taken up by the upper chamber.

“The trial could start and a senator could make a motion to dismiss (as Byrd did, unsuccessfully, in 1999) that would end it immediately,” Glassman adds. “Or a majority could move to table the articles of impeachment upon receiving them from the House and set a precedent that such a motion was in order.”

McConnell’s comments on CNBC also allude to the length of the impeachment proceedings, which is under Senate discretion. Typically, in an impeachment trial, witnesses are called and evidence is presented. Republicans could keep such efforts short if they wanted to move quickly to an acquittal.

As things stand, the Senate Republicans are expected to stand by Trump and acquit him if a full trial were to happen. For a conviction to actually take place, 67 senators would need to vote in favor, meaning at least 20 Republicans would have to join with the Democratic caucus.

Two presidents have been impeached by the House in the past, but the Senate did not convict either of them. For now, it’s not set to do so this time around, either.