Pfizer Inc.’s Viagra ushered in a pharmaceutical and cultural revolution, put the phrase “erectile dysfunction” in the medical mainstream. The first ads were sober, starring Bob Dole, then a 75-year-old former U.S. senator and ex-presidential candidate. The marketing started veering toward provocative in 2004, with the “Get Back to Mischief” campaign — the FDA asked Pfizer to pull some spots the agency deemed too suggestive.