A controversial remark by a prominent Democratic strategist about Ann Romney turned into a national debate on Thursday, leading even President Obama to defend Mrs. Romney and other stay-at home moms, saying in an interview “there’s no tougher job than being a mom.”

In an segment which aired on CNN Wednesday, Hilary Rosen, who is unaffiliated with the Obama campaign, had criticized the Romney campaign for highlighting the candidate’s wife in appealing to women, noting Mrs. Romney “never worked a day in her life.” Nearly everyone in politics of both parties, including top Obama campaign officials, quickly defended Ann Romney and criticized Rosen.

Here’s why this otherwise forgettable flap matters: women voters are critical in this fall’s elections. Women are a hard bloc to categorize in terms of electoral behavior because they are so diverse: there are conservative, liberal and moderate female voters, some who support abortion rights, others opposed. While the majority of women backed Obama in 2008, they are not like blacks, Latinos and voters under 30, voting blocs whose extremely enthusiastic support of Obama four years ago was unprecedented.

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But Obama performed better among white voters, both men and women, than previous Democratic presidential candidates, although he lost overall among both groups to Sen. John McCain four years ago.

Now, Democrats are trying to maintain those gains. In particular, Democrats are trying to distance female voters from the GOP by highlighting issues such as the Republican push for stricter abortion limits in states around the country.

One of the Democratic wedge issues on gender had been a measure called the Lilly Ledbetter Fair Pay Act, which Obama signed into law in 2009, that makes it easier for women to file lawsuits against their employers if they feel they have been unfairly paid less because of their gender. Obama’s team was hoping to highlight that issue this week, as Romney had not previously been supportive of the provision, which was opposed by most Republicans in Congress.

That’s why Rosen’s comment was costly for the Obama campaign. It’s unlikely most voters will remember the controversy over Ann Romney’s status as a stay-at-home mom on Election Day, or even next month. But it may prevent the Obama campaign from highlighting other controversial stands by Romney on issues that particularly affect women.

This article is the first in a series of pieces on “The Obama Coalition”: the key blocs in the electorate, such as African-Americans and voters between ages 18-30, that helped elect the first black president in 2008. We will examine if those groups are likely to support Obama again.

Follow Perry Bacon Jr. on Twitter at @perrybaconjr