Seeking to build a sense of urgency for November, First Lady Michelle Obama told a group of 400 campaign supporters in Iowa today that the election could come down to only a "few thousand folks."

"I just want you to remember that in the end, this all could come down to those last few thousand people that we register to vote. It could all come down to those few thousand folks we need to help to get to the polls in November," the first lady told the crowd of volunteers at a community center in Windsor Heights, a Des Moines suburb.

"I have said this before, Iowa, and you've heard me say it. He cannot do this alone. He needs you to help him," she said.

Obama's visit to the Hawkeye State - her second of the year - aimed to boost the campaign's efforts to keep blue what is seen by both parties as a key battleground.

President Obama's campaign has opened eight Iowa field offices and has volunteers organizing in each of 99 counties, officials said.

While Michelle Obama did not single out Mitt Romney by name, she exhorted her husband's Hawkeye State surrogates to emphasize his "core" of values when appealing to voters.

"All you have to guide you are your values and your vision and your life experiences," she said. " In the end when you're making those impossible choices, it all boils down to who you are and what you stand for - and we all know who my husband is."

As she did at a campaign fundraiser in Omaha, Neb., earlier in the day, Obama told supporters the stakes in the election are high, with the administration's accomplishments "all on the line."

"That's what you need to tell people with ever door you knock on, with every call you make, with every conversation you have. You need to tell people our values. Tell them everything that's at stake next November," she said.

"You tell them how Barack was for tax cuts for working families and small businesses. … Remember Barack had the backs of American workers."