WASHINGTON — Former Rep. Lindy Boggs of Louisiana — who used the soft-spoken grace of a plantation lady to fight for civil rights for 18 years in the House after succeeding her late husband, Thomas Hale Boggs — died yesterday. She was 97.

Boggs, who was ambassador to the Vatican in the Clinton administration, died of natural causes in her Chevy Chase, Md., home, said her daughter, ABC News journalist Cokie Roberts.