Why the polls are tightening up

But there may be something to learn from CNN/ORC’s decision to whittle their sample down to likely voters. The Clinton campaign’s goal has been to replicate Barack Obama’s 51 percent coalition in 2012. Assembling that coalition relied on spurring turnout among black, Hispanic and young voters.

There are plenty of signs Clinton is poorly positioned to do that. Black turnout and Democratic percentage is likely to be down, at least slightly, from when the first black president was seeking re-election. Polls have shown Hispanics are less interested and motivated by this campaign than just about any other demographic group.

Young voters, while repelled by Trump, are not attracted by Clinton. She ran way behind Bernie Sanders among young women as well as young men in primaries and caucuses. Four-candidate polls typically show Clinton running far behind the 60 percent Obama won among under-30s in 2012, with as many as 20 percent preferring Libertarian Gary Johnson or Green candidate Jill Stein.

So turnout could tilt more Republican this time.