Even Republican studies have

[svelte]

Even Republican studies have shown attacking Hillary on her husband, her age, her stamina, her health or her looks does not work.

http://www.politico.com/story/2016/10/donald-trump-bill-clinton-attacks-republicans-229760

And what does Trump choose to emphasize?

His policies? What he’ll do as president? No, he focuses on Hillary’s husband and her health.

A 300 pound doofus.