Republican Senator Rubio running for president: US media

Senator Marco Rubio announced to donors Monday that he is launching a US presidential campaign, becoming the latest -- and youngest -- Republican in the race to succeed Barack Obama in the White House. The 43-year-old first-term senator aims to contrast himself with older contenders like fellow Floridian Jeb Bush, his 62-year-old mentor-turned-rival for their party's nomination, and Democrat frontrunner Hillary Clinton, 67, who announced her candidacy on Sunday. Bush, who expected to offici