Former President Trump has been accused of incitement of insurrection, a serious crime defined by 18 U.S. Code § 2383. The law, as written, states as follows: "Whoever incites, sets on foot, assists, or engages in any rebellion or insurrection against the authority of the United States or the laws thereof, or gives aid or comfort thereto, shall be fined under this title or imprisoned not more than ten years, or both; and shall be incapable of holding any office under the United States."
This will be a question that every U.S. Senator will have to confront. At the beginning of the trial, all 100 Senators swore an oath before God to do impartial justice. At the end of the trial, all 100 U.S. Senators will have to cast a vote, which will ultimately determine whether Donald Trump is held accountable for what transpired on January 6th. Between those two points, the House Impeachment Managers will make their case.
President Trump was impeached on January 13th, 2021, while he was still President of the United States. Impeachment is a legal statement of charges, similar to an indictment in criminal law. The Article of Impeachment was subsequently delivered to the U.S. Senate on January 25th, 2021, several days after Trump's term had concluded. According to the Congressional Research Service, "most scholars who have closely examined the question have concluded that Congress has authority to extend the impeachment process to officials who are no longer in office."
The Senate will vote to determine whether he should be barred for life from ever being able to hold public office again.
In theory, the Representatives in the House are serving their constituents, and their vote to impeach President Trump may be political in nature. However, once an impeachment has been passed by the House, it is delivered to the U.S. Senate where the trial takes place. All 100 senators swear an oath before God to do impartial justice. In theory, each Senator should vote based on their own personal conclusions about guilt and/or innocence in accordance with that oath. In practice, during President Trump's first impeachment, the vote proved to be largely partisan in nature, with Mitt Romney proving to be the only Republican Senator to willing to vote against President Trump. Romney explained the reason he had to vote against President Trump was because as a deeply religious man, he took his oath before God seriously.
“I solemnly swear (or affirm, as the case may be) that in all things appertaining to the trial of the impeachment of President Donald John Trump, President of the United States, now pending, I will do impartial justice according to the Constitution and laws: so help me God.”