It's called psy-ops. Trump is winning in landslides and is a real threat to the Dems (probably Hillary, could be Sanders). So, to try to take out the threat as early as possible, the media runs bogus polls showing that Cruz beats Hillary, and no one else comes close. We, the voters, are supposed to see that and switch our vote from Trump to Cruz without logical analysis. If enough people do that, then Hillary faces off against a weak opponent and wins handily.
It is a sad reality, but this tactic works. It gave us Romney, McCain, and Dole. Each one of them was supposed to be the only candidate who could beat the Democrat, and each one went down in flames.
I remember 2008 when the mantra was that the Democrats really feared McCain. He was the man that could win because so many Democrats liked him and thought he was a reasonable Republican. Talking head shows fawned over him. He was a media darling.
Once he was nominated, the gloves came off and Oprah and her audience weren’t swooning over him anymore.
To a large extent, that was also true of Romney. But Romney actually should have won. In retrospect, picking Paul Ryan as VP was a weak move.
Kasick bases his entire political reality upon cooked polls.