Everybody agrees Romney won the first debate, and it wasn't even close. In order to get back to where he was with the voters before the first debate, President Obama needed a clear win on debate number two, needed to clearly defeat Romney - it didn't happen.
Did Obama do well enough to stop his continuing erosion in the polls? Maybe. But not well enough, I think, to gain back lost ground.
In boxing terms, Obama gave the first round away, tied the second round, and is unlikely to catch Romney napping in the third round - in other words, another near-enough tie. When the officials (i.e., voters) add up their scorecards for the match, no knockout but Romney wins on points.