The right looks at Chris Christie and likes what it sees. Naturally, the left looks at Chris Christie and hopes that he isn't as popular as Republicans think.
There's some support for both views. Republicans point out that Chris Christie has got the public on his side on the major issue facing the state: raise taxes, or cut spending, to cover its sizeable budget shortfall? The Democrats point to falling poll numbers and argue that his brand of confrontational, no-nonsense politics has failed.
I'd just point out that Chris Christie just finished his first year as governor in a state where ugly budget problems offer extremely unpleasant choices. He's made real, deep cuts, as he's had to--unlike Obama, to whom he is now being compared, he can't just borrow money to paper over the holes. Frankly, I'm surprised that his approval ratings are as high as they are. I expect that Andrew Cuomo is going to go through a similar cycle in his first year as governor, because if he holds to his pledge not to raise taxes (or even tries to kind of keep an eye on it from not too far away), he too is going to get into some really ugly battles with the public sector unions--and with the people who consume the services that the public sector unions provide.
A recession, or its lingering aftermath, is always the worst time to raise taxes or cut services. When the economy and employment are growing, people who lose jobs can generally go get another one. But when the pie is shrinking, someone has to actually give something up. Unfortunately, somehow, the necessary structural reforms never are taken until there's a crisis. That means the guy who presides over those reforms is going to take some heat.
But that hardly means you can count Christie out as a political force. Ronald Reagan's popularity dropped in the early eighties for much the same reason. Christie has three years for things in New Jersey to get a bit better.