That's exactly why I'd call it a stab in the back and a copout. There's a lot to be admired about giving to an underdog candidate on principle, even if you think that candidate will probably lose and even though we may support the other guy. But there is almost no such thing as principle on the 'Rat side nowadays. It's win or you're not worth a dime.
By contrast, look at Dinesh D'Souza giving to his friend Wendy Long, and having to pay a steep price, despite the fact he probably thought deep down inside she would likely lose.
Just think of where horse racing would be if nobody bet on the underdog(s).
Agreed, especially that we should support an underdog on principle. Plus, there HAVE BEEN political upsets, so we should never give up on really good candidates.