Polling experts say there’s reason for the president to feel encouraged — but also to think that there’s a limit on how much more he can improve.
For one, the range of the president’s approval rating over the course of his presidency has been smaller than any modern president with the exception of Gerald Ford, says Charles Franklin, a Marquette University professor and the co-founder of Pollster.com. 

His numbers have rarely inched above the low-50s, and rarely fallen below the low-40s.

Stalwart support from Democrats has provided Obama with a solid floor. But he appears to have an equally impenetrable ceiling, thanks to unflinching Republican opposition. 

Obama’s most recent gains can be attributed to improvements among some Democrats and independents. Further gains might be hard to attain.