WASHINGTON — Barack Obama, the U.S. Senate candidate from Chicago who has become the Democratic Party's latest rising star, is drawing enough support from the entertainment industry to put on his own variety show. From comedian Chris Rock to singer Barbra Streisand to musician Herbert Hancock, entertainers have written out checks of $1,000 or $2,000 to help the 42-year-old Illinois state senator win the seat being vacated by retiring GOP Sen. Peter Fitzgerald. Film directors Rob Reiner ("The American President") and Edward Zwick ("The Last Samurai" and "Courage Under Fire") both contributed in the past three months, according to Obama's...