(WSIL) -- Former President Donald Trump is facing an unprecedented second impeachment trial in the Senate.
There have only been four senate impeachment trials in U.S. history, including two against Trump.
The latest trial is the most unique, according to John Jackson, a visiting professor at the Paul Simon Public Policy Institute in Carbondale.
"It involves the public," Jackson said. "All of those others were what went on behind closed doors."
A single article of impeachment accuses President Trump of inciting a mob that violently stormed the U.S. Capitol on January 6.
"The senators and the members of congress from the house were all there," Jackson said. "They're sitting in judgment but they're also witnesses."
President Bill Clinton's impeachment trial in 1999 saw him accused of misuse of power. Lawmakers accused President Trump of bribery in the 2020 trial. The Senate acquitted both men.
"I don't think there are going to be 17 Republican senators cross over," Jackson said. "I'd be amazed if they did."
Jackson says the closest Congress came to a bipartisan impeachment vote was the Nixon Administration. President Richard Nixon resigned before the House could hold a vote.
The second trial against Trump may set the tone for future administrations. Jackson says this trial helps keep impeachment as an option to control the behavior of future presidents.
"It may embolden future presidents because they recognize that the odds of them getting impeached are very small," Jackson said. "I think that's the fear."
President Andrew Johnson was the first to be impeached in 1868, and was later acquitted. One of the house impeachment managers in that trial was U.S. Rep. John A. Logan (R) of Murphysboro.