Democratic mayors from four sanctuary cities are preparing to testify before the House Oversight Committee on Wednesday.

Denver Mayor Mike Johnston will soon be on his way to Washington D.C. to testify before the U.S House Oversight and Government Reform Committee to explain the city’s “sanctuary jurisdiction” policies.

Republican members of Congress hammered four Democratic mayors about their so-called sanctuary city policies, accusing them of endangering Americans and threatening to prosecute local officials.

Rep. Paul Gosar clashed over immigration with big city Democratic mayors in a congressional hearing, going as far as to quiz them on Arizona’s controversial Senate Bill 1070 law. The House Committee on Oversight and Government Reform hearing,

She stood up for the city and refused to cower in the face of threats and smears,” one of more than 1,700 respondents said. The post Mayor Michelle Wu represented Boston well at the ‘sanctuary cities’ congressional hearing,

Here's a rundown of several key claims made during the hearing, and our reporting on the issues and numbers referenced by officials.