Obama is sending them on that course with his joke about a guy born in Calgary running for POTUS.
It’s kind of a moot point at this juncture. If current trends hold, neither the dems nor anyone else need to concern themselves with Cruz winning the nomination. Sufficient numbers of GOP voters are making the strong statement they’d rather drive the Trump Train all the way into the river in November.
Don't kid yourself. You cannot 'unring' a bell.