Perhaps you can look up Pres. GHW Bush's campaign against Gov Clinton in 1992.
They (the Republicans and Pres. Bush himself) went out of their way to point out all the character flaws in Clinton ~ "the commander of the Arkansas National Guard" is how Pres. Bush derisively called him.
Clinton won... not by responding in kind (because that would have been futile), but by ... well, you know the game !!
His years as a POW are years we need to investigate. Did he help the enemy? Did he inform? Were there any embarrassing sexual trysts while imprisoned? Did the he drop napalm on unarmed civilians? If so, then he is a war criminal, and must be called out as such.
There are not very many ways of ensuring a McCain landslide...but that is one of them!