Let us begin by establishing that public discussion of presidential penis size was not invented by Donald Trump or Marco Rubio, nor is it a particular fixation of Republicans. Within memory are tales of Democrat Lyndon Johnson, who felt even more emboldened on the subject. No less an authority than Robert Caro informs us that "he would sometimes swing around still holding his member, which he liked to call 'Jumbo,' hooting once, 'Have you ever seen anything as big as this?,' and shaking it..." Seems a reasonable question in the context of the Vietnam War.
In fairness to Johnson, this did not occur at a presidential debate in front of millions of Americans. Whether or not that distinction matters is, well, for you to decide.
Given this bi-partisan history, we can safely turn to the question of why it matters.
It's a metaphor for something else. Toughness for example. Rather than say "I will commit troops to a ground war in the Middle East," which is controversial, say about your penis, "There's no problem down there. I guarantee it." Same thing, but less offensive to the warrior class and neo-cons.
But this raises more questions than it answers. Can we trust Trump about this? Remember, Mitt Romney believes "dishonesty is Trump's hallmark"; Cruz assures us that Trump "break[s his] word." Rubio: Trump is "lying", a "fraud" and a "con man". Oh my God, there's a problem down there and Trump is lying about it!
Republicans cannot let such a central part of their presidential contest remain unresolved. Truth Squad time.
Let's leave the press out of this, they have enough on their plate. We're unlikely to get a volunteer. So who's the Checker-In-Chief? Given the intensity of their respective challenges to Trump's honesty, I think Marco Rubio wins.
So we've established that this is important, that there's a real controversy and that Rubio has earned the opportunity to put up or shut up.
Don't hearken back to simpler times -- it misses the point. Trump is the only candidate who has read the mood of the Republican electorate accurately. He's right on point. What Republican voters want is the candidate with the biggest penis. Temperament or policy? Nah. No more talk of brokered conventions, or Establishment candidates, or the Koch Brothers. Wham. Here's your candidate and everyone will abide by the result, cause it's fair.
Is it good for the country? Could be. What's the alternative? Do you actually want to sit through more debates? And there isn't any big difference between them on tax policy, abortion rights, military involvement or immigration.
How about the Democrats? No written response needed.
Jonathan Swift once wrote a piece he entitled A Modest Proposal which argued that cannibalism would solve the problems of Ireland. A fair number of people didn't realize it was a satire. That's what happens when reality becomes malleable, and the people with real brains give up.
So go get'em Marco. Inquiring minds want to know.