> Instead, I see people twisting themselves in knots to defend positions they would normally denounce.

This is actually a rational behaviour (in an f-ed up system/incentive).

Any admittance of failure will be used against your candidate, and the opposition will defend their candidate just as strongly. Consider how when celebs get involved in scandals their PR isn't always to admit fault.

Its the same thing of "repeat a lie enough.."; even if the defence itself is not accepted, it can still soften the blow of the scandal by resisting the death-blow of unanimous condemnation. Humans are sometimes herd creatures, visible support is a universal defence in itself, even if only to threaten/dissuade attackers.

In other words, this is how political theatre works.