Let's look back on the primary campaign -- completed for Republicans, still ongoing for Democrats -- and see if we can identify what Sherlock Holmes referred to as dogs that didn't bark.
For what's unusual about this campaign is not only that unexpected things happened -- improbable candidates Donald Trump and Bernie Sanders getting more than 40 percent of their parties' popular votes -- but that things everyone has come to expect did not.
One clear example is the declining salience of the abortion issue. For a quarter-century this has been a litmus test for both parties' presidential nominations: Republicans wouldn't seriously consider pro-choice candidates; Democrats wouldn't seriously consider pro-lifers.
Much less has been heard about it this year. Donald Trump's conversion to pro-life got perfunctory mention, but clearly didn't sway many voters. Neither did Hillary Clinton's pro-choice fealty.
Why? The issue seems to be settled, in a way most voters find tolerable. Abortion is not going to be criminalized, but it is increasingly stigmatized. The abortion rate peaked in 1980, and the absolute number of abortions has been declining since 1990.
Abortions, like divorces and extramarital births, are rare among upscale Americans; they've become a mostly downscale phenomenon. Abortion clinics are closing, due to lack of demand as well as restrictive state laws. The procedure is disfavored in medical schools, where about half their students are women.
"Choice" -- the brilliant euphemism for abortion -- is not rallying voters to Clinton like her strategists had hoped. For women of a certain age, the abortion issue is a proxy for other choices they have made that run contrary to how they were brought up.
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These women have been giving Clinton big margins over Sanders. But younger women, raised to assume they should work outside the home, have voted heavily for Sanders. It's not clear they'll rally to the polls for Clinton in November.
If women have not been united among Democrats, evangelical Protestants have not been united among Republicans. Mike Huckabee and Rick Santorum, big winners among evangelicals in 2008 and 2012, had almost no support, even in Iowa, which they both won. Evangelicals voted in large numbers for Trump as well as Ted Cruz and Marco Rubio.
One reason is the vast change of opinion on same-sex marriage, now supported by about one-third of Republicans and clear majorities of all voters. Religious conservatives dismayed by this may simply be turning away from politics or voting on other issues. You didn't hear candidates boasting they were the strongest gay-marriage opponents.
Also largely missing from this year's campaign have been foreign policy appeals, which have prevailed in the past. Sanders berates Clinton for her 2002 vote authorizing military action in Iraq, but with less effect than Barack Obama had in 2008. Trump accuses the last Republican president of lying us into war and wins the party's nomination nonetheless.
You heard some Republican candidates vow to vanquish the Islamic State terrorists in Iraq and Syria, but none proposed anything like the massive military efforts launched in 1991 and 2003, much less "nation building."
Nor has there been much talk from the three remaining candidates about honoring the nation's commitments to NATO or our Asian allies. What you have heard from all three is a repudiation of free-trade policies followed by administrations of both parties since the 1930s.
From all three you've heard moaning about today's economy -- and total unawareness that policies they oppose have over the last 70 years built a world of increasing prosperity and growing freedom.
Trump talks vaguely of "making America great again," a backward-looking slogan that invites voters to imagine some time when everything worked. But a trade war doubling all prices at Wal-Mart isn't going to get us there.
Clinton has allowed Sanders to push her left on the Pacific trade agreement, the Keystone XL pipeline and Social Security: She now wants to increase already undeliverable benefits. As for promises of free college and health care, the experience of the last 30 years shows that pumping government money into these sectors only makes them more expensive.
A case can be made that old issues have become stale: No reason for the old dogs to bark anymore. But they've been replaced by a different kind of barking or braying -- angry rhetoric, nostalgia for imagined pasts and litanies of laughably unrealistic policies. That's not a step forward for America or the world.
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