The Missouri senator tells the Huffington Post:

"I think for Washington party insiders to come in and try to invalidate the votes of Missourians would be radical," McCaskill said. [...] "I think that would be a very radical thing to have happen, and I can't imagine how the Republican primary voters would think about that in Missouri."

 

"I think there would be a significant backlash," she added. "I'm not sure that would have a good ending for the Republican Party."

Clearly, her only concern is the stability of the Republican party and the integrity of the political process.