Benen was born and raised in Miami, Florida, and received his B.A. in Political Science from Florida International University. He received a master's degree in Political Management from the George Washington University, and was an intern in President Bill Clinton's White House.
In 1996, he was the communications director for an unsuccessful Democratic congressional campaign in Pennsylvania. From 1997 to 2002, Benen worked as a staff writer at Church & State magazine, published by Americans United for the Separation of Church and State.
From August 2008 to January 2012, Benen was the lead blogger for the Washington Monthly's "Political Animal" blog. He was the publisher of the political blog The Carpetbagger Report for five years and was the lead editor of Salon.com's Blog Report.
Benen's articles and op-eds have appeared in a variety of publications, including The New York Times, the Washington Monthly, The American Prospect, The Huffington Post, and the New York Daily News. He has been a contributor to Talking Points Memo, Crooks and Liars, The Guardian, AlterNet, Political Wire, and Seven Days.
He has been a guest on several radio and television programs, including NPR's Talk of the Nation,MSNBC's The Rachel Maddow Show, MSNBC's The Ed Show, MSNBC's Martin Bashir, MSNBC's Live with Thomas Roberts, Current TV's Countdown with Keith Olbermann, Air America Radio's The Sam Seder Show, and XM Radio's POTUS '08.
In July 2009, The Atlantic named Benen one of the top 50 most influential political commentators in the United States. In 2012, Benen wrote the introduction to the e-book, "Elephant in the Room: Washington in the Bush Years".