[DesertRhino]

“Trump was asked whether he would pledge to support the GOP nominee (after raising the potential for an independent bid in numerous interviews); “

That old saw again? Trump mentioned doing that only when the GOPe was conspiring to keep the solid frontrunner in the 5 main polls out of the debate. He never once suggested that losing an honest election would lead him to do that. He was in the debate, so the question was designed as a smear.
The honest question may have been, “what do you think of the GOPe big donor efforts to keep you, as the frontrunner, out of the debates?”

[Cowboy Bob]

The last Republican to run as a 3rd party candidate was Congressman John B. Anderson. He was a RINO who opposed Reagan. I don't recall hearing the MSM complain about his 3rd party run.