The second impeachment trial of Donald Trump raises legal questions that have no definitive answers — and that means senators will ultimately have to settle the issues for themselves.

The impeachment over Trump’s role in the Jan. 6 mob attack on the Capitol has prompted debate: Can the Senate hold an impeachment trial for a former president for actions taken while in office? Do the articles of impeachment have to include a crime? Does the chief justice of the United States preside over the trial? Can a former president be barred from holding office again?

Those issues will likely play a decisive role in the impeachment trial, scheduled to begin the week of Feb. 8. Some senators will lean on them to explain their vote on whether to convict Trump on the impeachment charge of incitement of insurrection, and maybe on whether to disqualify him from ever holding office again.

But there is no set of instructions or requirements for this situation, no matter how much history the members of Congress search through or how many times they read the text of the Constitution that set up this whole impeachment process, legal and congressional experts say.

The Constitution gives Congress the power of impeachment, and it’s up to senators to wield it. Senators don’t have to find the right answer, they just have to find an answer that is plausible, and it can be one used more for support than illumination, University of Texas law professor Steve Vladeck said.

Take the question of whether a former president can be convicted on an impeachment charge, one that is poised to be decisive for a number of Republican senators.

The Constitution does not directly address that. And though scholars have widely accepted that Congress can do so, the “text is open to debate,” the Congressional Research Service wrote in a “Legal Sidebar” this month.

Those scholars have their reasons: that the Senate did just that in 1876 for the impeachment of William Belknap, who had just resigned as war secretary in the administration of President Ulysses S. Grant; that this is what the framers intended for impeachment; that a president shouldn’t be able to avoid punishment for misbehavior by resigning just before a conviction.

With Belknap, the Senate debated and voted that it could hold an impeachment trial even though he had stepped down just before the House impeached him. But not enough senators voted to convict him, with some voting to acquit because they believed the Senate lacked jurisdiction over someone no longer in office, the CRS report notes.

The current Senate is not bound by the decisions of past Senates, and its decision now won’t necessarily bind a future Senate to come to the same conclusion, experts say.

A large enough group of Republican senators similarly could decide that the Constitution talks about removal of a current president only and vote to acquit based on the idea that the Senate does not have jurisdiction to convict a former president.

“Nothing stops them, and nobody gets to review it,” said Frank O. Bowman III, a law professor at the University of Missouri and author of “High Crimes & Misdemeanors: A History of Impeachment for the Age of Trump.”

Texas Sen. John Cornyn is among Republican senators who have argued ahead of the trial that the Senate doesn’t have jurisdiction to convict Trump on the impeachment charge of incitement of insurrection.

“No evidence impeachment of a former President, now a private citizen, was ever contemplated by founders, and they didn’t explicitly provide for it,” Cornyn tweeted. “Also, can’t imagine them embracing an open ended procedure to pursue political opponents.”

On the other hand, some experts predict Trump could go to the courts if Republicans appear to think the Senate does have jurisdiction, as he and his allies did with his failed attempt to overturn the results of the 2020 presidential election.

“Going to be fun when Trump asks SCOTUS to stop the impeachment trial. Wheeee!” tweeted Eric Segall, a law professor at Georgia State University who has written books about politics at the Supreme Court.

Segall is among experts who think the Supreme Court wouldn’t agree to hear the case, which would put it right back in the Senate’s lap. Or if the justices did agree to hear the case, they would decide it is a political question and that the Senate should decide.

Chief Justice John G. Roberts Jr., a George W. Bush appointee who has tried to keep the Supreme Court from appearing political or stepping into the role of the political branches, has already tried to stay out of the way.

Majority Leader Charles E. Schumer of New York said in an interview Monday on MSNBC that “it was up to John Roberts whether he wanted to preside with a president who’s no longer sitting, Trump, and he doesn’t want to do it.”

Instead, Democrats will have Vermont Democratic Sen. Patrick J. Leahy, the Senate president pro tempore, preside.

Iowa Republican Sen. Charles E. Grassley told reporters that Roberts not presiding “sends a pretty clear signal” of what the chief justice thinks of this proceeding.

The Constitution says the chief justice “shall preside” over the impeachment of a president. But it doesn’t say what to do with a former president, and Kentucky Republican Sen. Rand Paul is among those who will use that to argue that the process is unconstitutional.

“I object to this unconstitutional sham of an ‘impeachment’ trial and I will force a vote on whether the Senate can hold a trial of a private citizen,” Paul tweeted Monday. “Republicans should reject any process that involves a partisan Democrat in the chair instead of the Chief Justice.”

Not all Republicans agree, however.

Alaska Republican Sen. Lisa Murkowski told reporters Tuesday that she believes the trial is constitutional, “in recognizing impeachment is not solely about removing a president, it is also a matter of political consequence.”