I’ve been under the impression that the twitter referencing Carson, simply noted he was “out”, not that he was resigning or leaving the campaign. In other words, he wasn’t getting the 20% of the votes which would make him the serious competitor, therefore the Cruz campaign would likely receive a percentage of the Carson supporters in their campaign.
The colloquialism is being spun to make Cruz look dirty, which in itself is the dirty politics,....which is why it’s being published by MSNBC, the author of dirty politics.
I don't understand how anyone with any familiarity with the situation would read that tweet and decide that it meant anything other than he was ending his candidacy.