In this Dec. 17, 2014 file photo, Sen. Marco Rubio, R-Fla. speaks on Capitol Hill in Washington. If he runs for president as expected, Rubio will have to outshine what is expected to be a large field of experienced Republican senators and governors. (J. Scott Applewhite/The Associated Press)
U.S. Senator Marco Rubio will make a muscular foreign policy a focal point when he announces his presidential candidacy on Monday, portraying himself as the Republican most ready to handle threats to America in a chaotic world.