Aiming to shore up support among women voters in critical swing states, the Obama campaign is out with a positive TV ad highlighting the first bill President Obama signed into law - the Lilly Ledbetter Fair Pay Act.

The Democratic-sponsored legislation extended the statute of limitations to allow alleged victims of pay discrimination to sue their employers. It fulfilled a promise Obama made during the 2008 campaign and repeatedly tops his list of accomplishments in stump speeches for a second term.

"The son of a single mom. Proud father of two daughters. President Obama knows that women being paid 77 cents on the dollar for doing the same work as men isn't just unfair," the narrator in the ad says over images of Obama as a boy with his mother, as a dad with Sasha and Malia, and other working women.

"So the first law he signed was the Lilly Ledbetter Fair Pay Act to help ensure that women are paid the same as men for doing the exact same work."

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In 2010, the most recent data available, women on average earned 77.4 cents for every dollar earned by men holding the same full-time, year-round job, according to Census data analyzed by the National Committee on Pay Equity. The gap was virtually unchanged from 2009, when it was 77 percent and 2008 when it stood at 77.1 percent, before the law was enacted.

Still, women's rights advocates have hailed the law for helping some victims of discrimination pursue their compensation claims in the courts.

The 30-second spot, titled "First Law," is entirely positive and does not mention Mitt Romney. It will begin airing today in seven battleground states - Colorado, Florida, Iowa, North Carolina, Nevada, Ohio and Virginia - the Obama campaign said.

Officials say it's the first in a series of ads that will "highlight President Obama's commitment to issues important to women and their families."

Women are seen as a critical voting bloc for Obama's re-election effort. And while the president has held an edge over Mitt Romney among the demographic, the gap has narrowed. The latest ABC News/Washington Post poll from mid-May showed Obama up 7 points among women, 51 to 44 percent, down from April's 57 to 38 percent.