Or, as the Times puts it:
The glow of national pride seemed to rise above partisan politics, as support for the president rose significantly among both Republicans and independents. In all, 57 percent said they now approved of the president’s job performance, up from 46 percent last month.Among GOPers in the Pew poll, 16 percent "approved" of Obama both before and after the death of bin Laden. The NYTimes poll has it differently:
The increase in Mr. Obama’s ratings came largely from Republicans and independents. Among independents, his approval rating increased 11 points from last month, to 52 percent, while among Republicans it rose 15 points, to 24 percent.It may be that the NYT/CBS poll is a bit later, so people have absorbed the death of bin Laden and thus we're seeing more of an "approval" effect. It's a reasonable hypothesis.