Although fans of Barack Obama are expressing concerns about the bounce that Mitt Romney has enjoyed since his successful debate performance against the president last week in Denver, what should really alarm the Democrats is the swing in one particular demographic that has been with the president all year long — the single women bloc.

Monday's much-discussed Pew Research Poll showed a dramatic turnaround in the race.

The new four-point lead (49 to 45 percent) that Romney now has over Obama overall (the previous Pew Poll had Obama up by eight points) is significant, but what's truly startling is that Pew shows Romney now tied with Obama among single women — a demographic that Obama has owned all of 2012. In September, Romney trailed Obama by 18 points with single women.