Since President Trump took office, there's been a wave of people calling for his impeachment.Harvard Law professor emeritus Alan Dershowitz has been a staunch defender against the Russia investigation and impeaching Trump. American University professor Allan Lichtman, who in 2017 wrote a detailing the case for impeachment, says his argument has only gotten stronger.Want to support 1A? Give to your local public radio station and subscribe to our podcast. Have questions? Find us on Twitter @1a.