One of the main reasons for Barack Obama’s fall in the latest polls, and John McCain’s rise is that white women are suddenly uniting behind the Republican nominee. In recent weeks, ‘McCain enjoyed a 20-percentage-point turnaround against Obama among white women, going from an 8-point deficit before the Republican National Convention to a 12-point advantage after it.’

Before the Republican National Convention, McCain was informed he had to do something to change the game. He was trailing Obama considerably among white women. ‘Pre-convention polls by Quinnipiac University, for instance, showed McCain with a huge “gender gap” in states like Ohio, Minnesota and Wisconsin, where his support among white women trailed his numbers among men by 20 percentage points, and in Colorado, where the spread was 30 points.’

These are all swing states McCain has to win in November.

Team McCain realized this, and decided something had to change. They had to do something that would change the pattern; they had to get white women on their side.

And so they chose Sarah Palin as McCain’s running mate.

Everything instantly changed. Suddenly white women had a candidate they could identify with, after Hillary Clinton. She was one of them; a mother (of five!), with her own career, trying to combine taking care of a family with earning a living.

Democratic pollster Celinda Lake calls them “Wal-Mart moms, or Wal-Mart grandmas” and says they are not so much undecided as conflicted in making their choice this year. Geoff Garin, a Democratic pollster who served as chief strategist of Hillary Clinton’s campaign in its final days, agrees. “Frankly, it’s because they are conflicted on Obama,” he says. “They’d like to vote for a Democrat, but they’re not sure Obama is the one.” The Democratic nominee has not yet made the sale with these female voters, in part because they have yet to be convinced he has the experience he needs, and also because they are more culturally conservative than he is. And there could be another factor, one that is harder for pollsters to measure. “They are more racially sensitive, honestly,” than younger and more educated women, says Lake.

With his choice of Palin, McCain “definitely caught their attention,” Lake adds. But whether this is merely a blip or a real trend has yet to be determined. Obama strategist Anita Dunn predicts there will be a “settling effect” in the polls, as the Democratic campaign brings more scrutiny to Palin’s record — drawing attention, for instance, to the fact that she once actively supported the now-infamous “bridge to nowhere” earmark that she now claims to have turned down. At a news conference Tuesday morning in Riverside, Ohio, Obama himself dismissed the latest polling numbers and predicted that women’s votes would shift again in the coming weeks, as they focus on which candidate is more likely to improve the education system, provide better health care and transform the economy. “Ultimately,” he said, “those are the issues I think that are going to make the greatest difference in this race.”

But just in case they don’t, Obama has become increasingly aggressive in challenging the GOP ticket’s efforts to co-opt his mantra of change. “You can’t just re-create yourself,” the Democratic nominee said Monday. “You can’t just reinvent yourself. The American people aren’t stupid.” But if he is going to win over the Wal-Mart moms, Obama is also going to have to make a stronger case for himself.

What goes for McCain, also goes for Obama; he too needs white women to support him. If not by large numbers, than at least enough to make the difference.