Matthews, who would have run as a Democrat, "had attended several meetings that had included Pennsylvania representatives as well as some major fund-raisers in the Democratic Party" last year, reports the New York Times, which broke the news.
The "Hardball" host ran for Congress in 1974 and was a top aide to House speaker Tip O'Neill; he would have had to leave his lucrative job to take up a 2010 campaign.
"There has been speculation that Mr. Matthews, 63, was flirting with a Senate run as a way to give him some leverage in his contract talks," reports Bill Carter. A previous report had suggested NBC wanted Matthews to take a $4 million pay cut in his new contract, to $1 million per year.
"Since that report, 'Hardball' has bounced back in the ratings, especially during the presidential election season, and NBC News executives have expressed much more interest in retaining Mr. Matthews," writes Carter.