Mason's first job was as a clerk in the Washington bureau of the Dallas Morning News, and In 1988 she went to Texas to work as a reporter with the Houston Chronicle. She was transferred to the newspaper's Washington bureau in 2001 but was laid off in 2008 while serving as the paper's White House correspondent. She worked at the Washington Examiner as a White House reporter until 2010, when she joined Politico's White House team. She joined SiriusXM in 2011. In 2014, Mason received the Gracie Award from the Alliance for Women in the Media for outstanding achievement as a radio talk show host. She has been the secretary and a board member of the White House Correspondents' Association.
One report said that Mason is known for her "bawdy personality and quick wit." Television commentator Bill O'Reilly in 2014 called her a "loon" because, according to him, she suggested that he and Glenn Beck may have damaged the Fox News "brand."
In 2011, White House press secretary Jay Carney called one of Mason's stories "partisan, inflammatory and tendentious," and U.S. National Security Council spokesperson Tommy Vietor sent her an e-mail that included an animated picture of a crying mime, a "visual suggestion that she was whining," according to Washington Post columnist Paul Farhi.