President Obama has been mostly somewhat above 50% and occasionally drifting somewhat below - with a few outliers. The media has mostly reported when it went down - which could have lead some to thing he has continually fallen.
But, here is what they say of Christie:
"In spite of the battle with educators, Christie's job approval rating among registered voters stands at 42 percent, with 44 percent disapproving. That compares favorably to his predecessor, Jon Corzine, who had a 34 percent approval versus 37 percent disapproval rating at the same point of his first year in office."
http://www.dailyrecord.com/article/20100413/UPDATES01/100412143/1005/NEWS01/Poll++Christie+takes+most+blame+for+teacher+layoffs+%E2%80%94+not+unions+or+school+boardsThe fact is that saying he was better than Corzine at this point is almost like dividing by zero, it doesn't same anything about the numerator (or the person being compared) At this point in Corzine's term, he was dealing with the story of his negotiating with a top union boss, who was his former girlfriend, who he had given millions to when they split. It was also soon after an election where his ex-wife made a commercial against him.
The fact is that being at 42 percent now is not good. Sure, he can regained popularity, but his electoral history was that after he won a Morris County freeholders'seat, the next election the republicans put up 4 candidates for the three seats - and he lost in the primary.