... if that candidate is male, anyway, is a beard.
From 1860 to 1913, only two presidents (Andrew Johnson and William McKinley) were clean-shaven. Then, as quickly as it had come about, the "presidents must have beards, or at least mustaches" standard went away. The last major party presidential candidate to wear a beard was Charles Evans Hughes in 1916. A mustache, Thomas E. Dewey in 1948.
But beards and mustaches seem to be back in a pretty big way the last few years.
It's not a big deal, mind you, but if I was looking at two candidates who were equal in all other respects, I'd pick the guy with the beard over the guy without one (although, frankly, I'd probably pick a woman with the same qualifications over either of them).