Barack Obama and his allies promised to make this election about the 47%, and so far they’re succeeding — but in a much different way than they expected.  In most of the latest national polls, Obama can’t get above 47%, while his challenger Mitt Romney surpasses him.  Add the Politico/GWU Battleground poll to the list, where Romney moved into the lead for the first time:

Mitt Romney has taken a narrow national lead, tightened the gender gap and expanded his edge over President Barack Obama on who would best grow the economy.

A new POLITICO/George Washington University Battleground Tracking Poll of 1,000 likely voters — taken from Sunday through Thursday of last week — shows Romney ahead of Obama by two points, 49 to 47 percent. That represents a three-point swing in the GOP nominee’s direction from a week ago but is still within the margin of error. Obama led 49 percent to 48 percent the week before.

Romney has not led in the poll since the beginning of May.

Across the 10 states identified by POLITICO as competitive, Romney leads 50 to 48 percent.

Let’s take a look inside the numbers.  The D/R/I for this poll is 35/31/33 for a D+4, a not-insupportable number that probably still understates Republican enthusiasm and turnout.  Republicans comprised 32% of the electorate in 2008 and 35% of the electorate in 2010, so they’re unlikely to have a worse relative turnout this time than either of the past two elections.  However, the non-white percentage in the sample (22%) looks a little thin compared to 2008 (26%), but close to 2010’s 23%.  That’s something to keep in mind, as I suspect that the 2012 turnout will be somewhere between the two, and the undersample here may balance out the undersample of Republicans.

Two keys suggest Romney’s doing better than his toplines.  First, he’s winning the gender gap.  Romney gets a +10 among men, while Obama gets a +8 among women, for a +2 advantage for Romney.  In 2008, Obama had a +14 gender gap advantage over John McCain.  Obama wins single women, but is getting clobbered among married women, 42/55.  Romney’s also leading among women without children overall, 50/46, suggesting that women who already know how to access birth control aren’t terribly concerned about it as an election issue.

The second key is age demographics.  Obama has a 30-point lead among voters 34 years and younger, but that’s his only win.  He and Romney tie among 35-44YOs at 48 each, but Romney has double digit leads among 45-64YOs (54/44) and seniors (58/38).  Those last two demographics are the most likely to vote in the election.

This is yet another poll series showing Romney trending toward victory, and I suspect that the momentum is greater than the toplines suggest.  Keep an eye out after the final debate as more undecideds firm up their choice — as history shows, they tend to support the challenger.  As Chuck Todd said yesterday, 47% is a bad number for incumbents, not challengers: