Democratic Congressman Alan Grayson has announced he'll seek the Senate seat Republican Marco Rubio is leaving to run for president. 

The decision announced Thursday guarantees a feisty primary between the unabashed liberal and U.S. Rep. Patrick Murphy, a former Republican who's running as a moderate and who has garnered the support of many party leaders. Grayson, who represents a central Florida district, made his announcement on Orlando television station WKMG. 

Grayson is known for his brash, unapologetic criticism of Republicans. While he's popular with the progressive wing of the Democratic Party, some party leaders are concerned he's too politically divisive to win a general election. 

Republican Congressman Ron DeSantis is also running with other GOP candidates expected to get in the race soon.