I'll give you Hillary, but she's a special case given her Husband's status as a prior POTUS. Romney was a presidential candidate from 2012 (not just a primary loser). There are numerous examples of the candidate of the losing party remaining in power. Just look at Al Gore. Although, I'd note that since Trump took office, Romney doesn't seem to wield much GOP influence/power. Bernie Sanders would be nothing more than another Rick Santorum this year if not for the email leak. At least that's my opinion.