Margolies, who's running in the Democratic primary race for Pennsylvania's 13th District, is the mother of Chelsea's husband, Marc Mezvinsky.
But Clinton has another reason to support Margolies. She held the 13th District seat back in 1993, and cast the deciding vote in favor of the then-president's controversial tax increases.
She lost her 1994 election to a Republican.
[Philadelphia Inquirer, Washington Post]
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