I think you're being too conspiratorial here. The reason why anyone who gets close to Mitt in the polls implodes is because all of the other candidates in the Republican field are fatally flawed in some way (so is Romney...but it's for ideological reasons instead of scandals/poor qualifications). Once the nation's attention is drawn to any of the others it's only a matter of time before that person tanks. Even if Herman Cain didn't have the sexual harassment mess, it was still only a matter of time before someone as inexperienced as him would have said something stupid to destroy his campaign.
As for the leaflets, I don't know if the Romney campaign has anything to do with them, but regardless I'd imagine there is a certain amount of conservative discontent with a man who has been married three times and resign in disgrace after an affair, all while running as a "family values" candidate. If he's worried about getting attacked by Romney just wait until he faces the Obama campaign and actual political enemies.
