Temporarily replacing one's own position with a more reasonable one in order to dodge criticism/refutation.

General form:
"B" (where one's initial statement was A)

Typical example:
"We should immedialy invade the neighboring countries before they decide to invade us."
"I think that's a really bad idea."
"I'm just saying we should defend ourselves; I don't see what's so wrong with that."

Once someone changes their original argument with another one, he has tacitally admitted being wrong. Even if the new argument is right, that doesn't make the former one also right.