Rep. Mike Castle (R-Del.) will hold a press conference at noon Tuesday at which he is expected to reveal whether he will run for an open Senate seat in 2010.Castle will speak in Wilmington, his hometown and the largest city in the at-large Congressional district he has represented since 1993. His office didn’t respond to requests for comment.Former Rep. Tom Davis — a former head of the National Republican Congressional Committee and close friend of Castle’s — said he wasn’t sure what Castle would do but that he talked to him last week and said Castle has been making preparations behind the scenes to get ready for a potential Senate race.Should he run for the Senate, Castle would become the early frontrunner for the seat currently held by Democratic Sen. Ted Kaufman, who was appointed early this year to succeed Vice President Joseph Biden. Kaufman is not running to serve the remaining four years of the six-year term that Biden won in November 2008, simultaneous to his election as vice president.A potential Democratic candidate is state Attorney General Beau Biden, the vice president’s eldest son who just returned to the state after finishing up a military obligation in Iraq as a captain in the Delaware Army National Guard. Beau Biden was elected state attorney general in 2006 and is up for re-election next year.Castle has already all but officially ruled out running for re-election to the House.