Donald Trump is expected to become only the third US president to be impeached by the House of Representatives. Democratic lawmakers are preparing to approve two impeachment charges against the Republican president. Mr Trump would then face a Senate trial next month, but members of his party control that chamber and are unlikely to remove him from office. The president has called the process an "attempted coup" and a "scam". In a six-page letter to the Democratic Speaker of the House, Nancy Pelosi, on the eve of the vote, the 45th president of the United States argued he had been treated worse than "those accused in the Salem witch trials". Mrs Pelosi described the letter as "really sick". On Tuesday, she wrote to colleagues that impeachment was "one of the most solemn powers granted to us by the Constitution", and called it a "very prayerful moment in our nation's history". Surveys suggest the country is split on the process. US political website FiveThirtyEight's collection of national polls shows just over 47% back impeachment, while 46.4% oppose it.