As soon as he started making the comparisons, Trump was forced to argue that going after the former president was "fair game" politically. It's hard to see why it wouldn't be. Bill Clinton is soon to hit the trail in New Hampshire on behalf of his wife -- as no doubt her strongest surrogate -- and will hardly be unprepared for dealing with the issue. Even allies of Trump's opponents have largely agreed that it's acceptable, while disagreeing on the attacks overall efficacy.
If you're reading this, the odds are very good that you're well acquainted with the issues we're talking about, culminating with Bill Clinton's affair with Monica Lewinsky, but actually stretching back to the early days of the 1992 primary. Trump's comments are academic in the sense that he's not opening your eyes about Clinton's behavior. But it raises the question: How many 2016 voters fall into that same camp?
Without surveying 2016 voters on the subject -- which doesn't appear to have been done (yet) -- we can only estimate. The Census Bureau releases annual data on the size of the population by age, the most recent of which is from July 2014. Assuming that the same number of people were born between July 2014 and July 2015 as in the preceding year, here's roughly how America's 320 million are distributed by age. Three-quarters are old enough to vote.
To figure out how familiar the population is with Clinton's personal foibles affairs, we need to figure out what we're talking about. There's Monica Lewinsky, of course, which played out primarily in 1998. At the front-end of his presidential bid were the 1992 allegations about an affair from Gennifer Flowers. So let's use those year markers to figure out how much of the current population lived through those events.
"Being alive" doesn't equal "remembering," as any 5-year-old can demonstrate. Let's peg the age of remembering-political-things-over-the-long-term at 11, mostly because an old study involved 11-year-olds. And because it seems about right.
The percentages of all Americans and over-18 Americans who were alive during Flowers and Lewinsky or who were 11-or-over looks like this.
More than half of people old enough to vote were also old enough to remember both the Flowers and Lewinsky affairs (to use both meanings of the phrase). About 73 percent of people over 18 were 11 or older when Flowers made her 1992 allegations. Eighty-three percent were old enough during Lewinsky.
But, let's be fair. How many 11-year-olds were paying rapt attention to the machinations of Kenneth Starr when they could instead be playing Pokémon (which is what 11-year-olds did in 1998, if I remember correctly)?
In 2009, Gallup looked at how much attention different age groups paid to political news. The older the voter, the more attention was paid. About a fifth of people under 30 followed political news "very closely;" 46 percent of those 65 and over did so. What's more, people overall were paying less attention to politics in 2001 than 2009 -- 26 percent to 36 percent of all adults said they paid very close attention. Which suggests that only a small percentage of people who were old enough to remember Lewinsky as it happened were paying attention.
We have better data than that, though. In December 1998, 70 percent of adults told Pew Research that they were paying very close attention to the impeachment hearings that surrounded Clinton in the wake of the Lewinsky revelations. In August of that year, a survey from Health News Interest Index broke down how much attention age groups were paying to the allegations against Clinton overall. A third of those under 30 were paying very close attention with another 29 percent paying "fairly close" attention. Eighty-two percent of those 65 and over were paying fairly or very close attention.
If we overlay that onto the old-enough-to-remember Lewinsky numbers we determined above, the percentage of people who were 1) old enough to remember and 2) actually paying attention looks like this. (For those ages 11 to 17 in 1998, we used half of the 18 to 29 figure.)
For the Flowers affair, the numbers are almost certainly lower. The revelations came during the Democratic primary, which necessarily means a smaller audience than a presidential impeachment, for example.
But this is also an underestimate from the standpoint that during the ensuing two decades (almost), anyone who wasn't aware of the events in the moment they happened has had the opportunity to become acquainted. It would be silly to assume that someone who was 5 in 1998 does not now, at the age of 22, know what happened when Bill Clinton was president. I like to jab at millennials as much as anyone, but I have to assume that some of this trickled down at some point.
Trump's attacks take for granted that people will know the broad strokes of what he's talking about. Even among the youngest voters, that's likely a safe bet. Which saves the uniquely-coiffed candidate from the vulgarity of having to explain his tweets.