At the start of the Labor Day holiday weekend — with Congress away, Syria looming large and many Americans consumed by back-to-school chores and last-gasp beach breaks –the politically savvy Cheney sisters publicly clashed over same-sex marriage. “I am strongly pro-life and I am not pro-gay marriage,” declared Liz Cheney Perry, who at 47 has a husband, five kids and a strong desire to defeat Wyoming’s three-term Sen. Mike Enzi in the Republican primary next August. She has cast her run against Enzi, 69, as generational.