U.S. Sen. Marco Rubio, R-Fla., is the target of a threat deemed credible enough to merit police protection in Washington, D.C., and at his home in West Miami, his office said late Tuesday. The freshman senator rocketed to national political stardom in recent weeks as he jumped to the top of the shortlist of potential running mates for presumptive Republican presidential candidate Mitt Romney. From CNN to The Daily Show, Rubio has become a staple of cable-news chatter about whether Romney will offer him the spot — and whether he would take it. But the fame has made him not...