One thing Obama urgently needs to prevent during tomorrow’s debate is this: He can’t allow Mitt Romney to become the candidate of change in this race. And that may be in the process of happening.

In an interview this morning, Dem pollster Stan Greenberg said he had identified a key reason Romney’s last debate performance was a success. To wit: Romney successfully grabbed the mantle of change agent, even as Obama came across as the candidate of the status quo.

“The danger for Obama is that Romney would become the candidate of change,” Greenberg said. “Obama has the chance in this debate to undermine that.”

Greenberg is releasing new research today backing up that point — and counseling Obama on how to prevent it from happening. Greenberg says dial sessions he conducted during the debate indicated that independents and unmarried women — two key constituencies — were unmoved when Obama talked about the progress of the last four years or when his surrogates said variations of: “Give him more time to finish the job.”

Greenberg says this risks painting Obama as the candidate of the status quo — and that this is dangerous even if people believe the economy is recovering. Greenberg’s national polling shows that people believe the middle class’s problems run so deep that recovery alone isn’t enough — large majorities say our problems can only be solved with “major changes.”

Romney is successfully exploting this, Greenberg says, with his heavy emphasis on his five point plan for the middle class, which also tests well in his polling. Romney has also made gains by contrasting that with the notion that continuing the status quo is unacceptable: “We can’t afford another four years like the last four years.”

This explains Romney’s gains. For months he operated from the flawed assumption that he could win by making the race all about Obama. Romney began surging only when he broke through at the debate with an affirmative case for his own agenda — because voters began entertaining the idea that Romney represents change, Greenberg says.

Obama was caught flat footed by this at the first debate, and didn't make a clear enough case that he would pursue major changes himself in his second term. This was in striking contrast to his successful convention speech, in which he did lay out a case for major second term change, via investments in clean energy, manufacturing, the auto industry and education.

Greenberg says his polling suggests the American people favor Obama’s vision of future change — when it is clearly defined for them. If it isn't, Romney will become the candidate of change in this race. “These are tough times — voters want to know that there is the possibility of real change, that the big issues facing the middle class will be addressed,” Greenberg says.

Obama also needs to aggressively debunk Romney’s five point plan as a bill of goods — as something we’ve seen before — but it’s crucial that he contrast it with a big-thinking second term change agenda of his own.

“It would be much more powerful if he says, ‘here are the serious things we need to do to rescue the middle class, but you should know that the plan you’re hearing from Romney is one you’ve heard before,’” Greenberg says.


UPDATE: Greenbrerg’s new research is right here.