FiveThirtyEight had confirmed that MSNBC’s Chris Matthews will run for United States Senate in Pennsylvania in 2010.

Matthews, 62, will run as a Democrat. Arlen Specter, the aging Republican incumbent, will be 80 if he chooses to run for re-election.

Update:

Chris Matthews has denied this report that he’s hiring staff for a Senate campaign in a statement posted on FiveThirtyEight.com, the site that originally reported the news. “It is absolutely not true,” said Matthews, in a statement.