SAN ANTONIO — Mikal Watts didn’t have a fighting chance — politics were in his life from the start. As a toddler, he rode in a stroller as his mother marched in a farm workers’ rights march in Austin. Politics made for dinner table conversation and filled the pages of books in the family library. He attended fundraising barbecues with his parents. Before the age of 18, he knocked on doors registering people to vote. In the years since, Watts has risen from law-school whiz kid (he received a degree at 21) to nationally known product liability lawyer and political...