DES MOINES, Iowa — Hillary Clinton won the endorsement Friday of the woman behind federal legislation making it easier for women to challenge their employers over unequal pay.

Lilly Ledbetter, namesake of the first law President Obama signed in 2009, said Clinton is a "fierce and uncompromising champion for women, for basic fairness, and for opportunity for everyone."

The Clinton campaign was announcing the presidential endorsement Friday, the seventh anniversary of the law loosening time limits for lawsuits over unequal pay. Clinton frequently invokes Ledbetter's story in her campaign speeches, and notes that women are typically paid roughly 20 percent less than men for the same work.

"We have got to have equal pay for equal work," Clinton said Thursday, as she campaigned in Iowa.

Clinton is locked in a tight race with Democratic  challenger Sen. Bernie Sanders four days ahead of the first presidential selection contest here, and women — particularly older women — are vital to her support.

Ledbetter worked for Goodyear Tire and Rubber for nearly two decades before learning that, as a rare woman in a senior supervisor role, she was making between $500 and $1,500 less each month than male counterparts. She sued, but the Supreme Court ruled against her because she had missed a short legal window to file a challenge. The 2009 law allowed lower paid workers, who are often women, to bring claims long after their pay is set.

"I was being paid significantly less for the same job — less than I deserved and less than my family needed," but didn't know it, Ledbetter wrote in an essay to be released by the Clinton campaign later Friday. A copy of Ledbetter's endorsement statement was provided by the Clinton campaign.

Clinton helped sponsor a law to negate the high court's ruling.

"Under this law, no one else will ever have to accept the gender discrimination I faced without the chance to challenge it in court," Ledbetter wrote.

"Hillary understands that these issues can’t be dismissed or pushed to the sidelines. They’re not just 'social issues' — they’re fundamental to our country’s economic future, and they are at the heart of everything she’s fighting for on this campaign," Ledbetter wrote. "For Hillary, this is about more than politics — it’s personal. She just gets it, plain and simple."