It comes from the term “cuckold”, which is the husband of an unfaithful wife, and it has been morphed into the term “cuckservative” which means-
“A cuckservative is a self-styled “conservative” who will cravenly sell out and undermine his home country’s people, culture, and national interest in order to win approval with parties hostile or indifferent to them.”
http://www.urbandictionary.com/define.php?term=cuckservative
It’s also got a nasty porn meaning that I think some of those who invented it on Twitter did intend to convey with it. For that reason, they were amused when Dana Loesh voiced the term. I try not to watch her if I can.