It also cuts into a large constituency of his, big enough to put Trump over the top.
I still prefer Cruz, but IMHO, this would be a master stroke, game over kind of thing for Trump.
It is - because Palin still has a support base, many of whom are not yet completely familiar with Cruz. Now, they may never take the time to become so.
Palin endorsed McCain, also - so this is not really out of character. She is a more mainstream Republican than the pundits seem to believe.