LITTLE ROCK, Ark.—One of Hillary Clinton’s first assignments as a corporate lawyer landed her far from her roots. She helped overturn a ballot measure that increased electric rates for businesses and lowered them for the poor.

“Instead of defending poor people and righting wrongs, we found ourselves squarely on the side of corporate greed against the little people,” her colleague, Webb Hubbell, later wrote.

The future presidential contender worked for 15 years as a corporate litigator at the Rose Law Firm in Arkansas’s capital, longer than any other position in or out of government. Her portrait still hangs in the firm’s downtown offices.

Yet that chapter in her life has been all but excised from the official Hillary Clinton story. She hardly ever mentions it on the campaign trail. Her husband skipped past it when telling of her life story at the Democratic National Convention. Until August, it wasn’t even mentioned on her campaign’s official biography.

It illustrates a pattern apparent through Mrs. Clinton’s career and into this year’s presidential campaign: She emphasizes different roles for different audiences. During her time in Arkansas, she was an advocate for children and families, and a successful lawyer at a white-shoe, mostly male law firm, representing the state’s biggest corporations.