During Trump's impeachment trial, Senator Mitt Romney became the first senator in US history to vote to remove the president of his own party.
During the impeachment trial, United States Sen. Romney said that he would vote against the second article of impeachment, obstruction of Congress, arguing that House Democrats had failed to exhaust their legal options for securing testimony and other evidence. But he said that Democrats had proven their first charge, that the president had misused his office in a bid to pressure Ukraine to investigate former Vice President Joseph R. Biden Jr. for political reasons. Romney became the first senator in US history to vote to remove a president of his own party in a Senate impeachment trial, noted the Guardian.
Subsequently, Donald Trump Jr. called for Romney to be expelled from the Republican party.
Before Trump, three other Presidents have faced impeachment in US politics - Bill Clinton, Andrew Johnson, and Richard Nixon. None of the senators belonging to these presidents' parties voted against them during the impeachment trial.
But, during Nixon’s impeachment, seven Republicans from the house voted for at least one impeachment article against Nixon in 1974. Ten Republicans voted against all three articles of impeachment. Both Clinton and Johnson faced impeachment trials, but they were not removed from office. When Johnson was tried in Senate, he held onto his presidency by a single vote, after seven Republicans decided to vote with Senate Democrats to keep him in office. When Clinton was tried, while many Senators agreed that Clinton had behaved badly, with regards to his affair with his secretary, they ultimately decided that his misconduct wasn’t at the level of “high crimes and misdemeanors.”