If Hillary doesn't make any mistakes, she will easily become the democratic party nominee and completely crush any republican that has the unfortunate task of running against her in 2016. The only exception might be Jeb Bush. He's probably the smartest guy on the republican side.
As for the other potential republican nominees:
Christie: His tough guy act is running thin and he's just oozing with corruption. His trip a few days ago to the UK
was paid in full by the King of Jordan. Illegal? YES! But Christie changed the law just days before. The guy has New Jersey-sized balls for sure.
Rand Paul : He MIGHT have had a chance, but his stupid and reckless Anti-Vax comments last week killed his chances. He's a fucking DOCTOR but he still lies through his teeth to pander to idiots.
Rubio : Seems like a smart guy and gave an impressive interview recently but I don't think he can stand up against Hillary.
Ted Cruz : 2016's answer to Sarah Palin and Michelle Bachman. Total dumb fucking idiot. Oops wait - as it turns out he's actually very smart, but says stupid, ridiculous things anyway.
Everyone else : Hardly a blip on the 2016 radar.
Sorry guys - Hillary will win, easily.