For now, the smart money is still sticking with Hillary Clinton. Since November, Donald Trump has moved up a slot and Marco Rubio has moved down. It's fair to say that Trump was always leading Rubio, but there was some expectation Trump would fade and Rubio would become the front-runner. Ted Cruz has also moved up, despite questions about his eligibility.
Moreover, Trump is poised to run the table in February:
|Candidate||Iowa2/1/2016||New Hampshire2/9/2016||South Carolina2/20/2016||Nevada2/23/2016|
That would put Trump's raw odds (if these were just coin flips) at 19% to run the table and win all four delegate contests in February. However, these are not independent events, and a sweep would create tremendous momentum going into the Super Tuesday primaries and caucuses in 13 states on March 1.
Update 2/2/2016:Trump didn't buy the farm in Iowa, but he did say he was thinking about buying one in his second place victory/concession speech. His odds of sweeping the remaining 3 contests in February has dropped to 13%. I'm guessing he saw his shadow in New Hampshire on Groundhog Day.