MOSCOW, Dec 14 (Reuters) - President Vladimir Putin warned on Thursday that some of his opponents would destabilise Russia and usher in chaos if they were elected in a presidential election next year, but promised genuine political competition. Putin, who is running for re-election in March, was answering a question at his annual news conference about opposition leader Alexei Navalny who looks unlikely to be allowed to contest the election due to what Navalny says is a trumped up criminal case. The question was put to him to Ksenia Sobchak, a television personality who has said she plans to run...