Several people Andrew Breitbart worked with -- and some he worked against -- expressed their condolences today after hearing of his .
Republican presidential candidate Rick Santorum called the conservative publisher and activist's death "shocking."
"What a powerful force," he said of Breitbart. "It's almost - you think of anybody out there who's just got more energy, and just, out there constantly, driving and pushing. What a huge loss, in my opinion, for our country, and certainly for the conservative movement." (Watch the comments in the video below)
Via Twitter, Mitt Romney said, "Ann and I are deeply saddened by the passing of @AndrewBreitbart: brilliant entrepreneur, fearless conservative, loving husband and father."
Newt Gingrich also gave his reaction on Twitter, saying, "Andrew Breitbart's sudden death is a tragedy for his family and for conservatism. Callista and I send our prayers and our condolences."
Sherrod released a statement in response to Breitbart's death, Talking Points Memo reports: "The news of Mr. Breitbart's death came as a surprise to me when I was informed of it this morning," she said. "My prayers go out to Mr. Breitbart's family as they cope through this very difficult time."
The liberal watchdog group Media Matters, which often clashed with Breitbart, responded respectfully, "Media Matters has a long history with Andrew Breitbart. We've disagreed more than we've found common ground, but there was never any question of Andrew's passion for and commitment to what he believed. Our thoughts and prayers are with his family today."
Liberal Huffington Post publisher Arianna Huffington recalled to Forbes working with Breitbart, who helped her launch the Huffington Post.
"All I can think of at the moment is what Andrew meant to me as a friend, starting from when we worked together -- his passion, his exuberance, his fearlessness," she said. "And above all, what I'm thinking of at the moment is his amazing wife Susie and their four beautiful young children. My love and thoughts are with them right now."
Matt Drudge, of the news aggregation site Drudge Report, also recalled working with Breitbart.
Drudge posted on his site's homepage, "DEAR READER: In the first decade of the DRUDGEREPORT Andrew Breitbart was a constant source of energy, passion and commitment. We shared a love of headlines, a love of the news, an excitement about what's happening. I don't think there was a single day during that time when we did not flash each other or laugh with each other, or challenge each other. I still see him in my mind's eye in Venice Beach, the sunny day I met him. He was in his mid 20's. It was all there. He had a wonderful, loving family and we all feel great sadness for them today... MDRUDGE."
On the House floor today, Rep. Steve King of Iowa called Breitbart, "dynamic, brilliant [and] fearless."
"His influence will be cascaded across this culture, I believe, in perpetuity, just like the influence of John Quincy Adams," said King.