Although there is no expectation that the Republican primary turnout will multiply by the same amount as before, to yield 70-90 million Trump voters in the general, it is still possible for the numbers to swell based on infrequent voters.
Normally these folks are sitting at home on Election Day, and may not even be registered. If any candidate in living memory could turn such people out for the first time in awhile, or ever, it's Trump. And with national turnout rates sitting at around 60%, that does leave a large chunk of the potential voters to become actual voters.
Now we have to ask where such people might come out of the woodwork. In other words, where are turnout rates the lowest? The map below shows turnout rates among the voting eligible population, with red being low and green being high, taken from this site:
First, the bad news. Most of the low turnout states are already safe red states, so even if Trump managed to send their abysmal rates soaring toward the maximum, it would not affect the state race or add to the Electoral vote count. Texas has a turnout rate of just below 50%, but it was already in the Republican's pocket before the race began.
The flipside is that most of the states with high turnout are blue states that we need to flip -- and if turnout is already fairly high, there isn't such a yuge pool of infrequent voters to tap into. Wisconsin's turnout rate is 73%, leaving far fewer infrequent voters to get out of the house, compared to Texas.
But the good news is that there are some exceptions, where a blue state has low turnout. These include the three central blue states of California, New York, and Illinois, with rates around the mid-50's. If the Trump campaign had enough time, money, and manpower, they could organize the unorganized in these states and make up even the sizable gap among the frequent voters.
However, these states have large populations, so it would probably be too much of a stretch to mobilize the legions of infrequent voters there -- we're talking millions of people in just two months. Some chunk will organize themselves by finding out how to register, where their polling station is, and show up on Election Day. But these self-organizers probably won't make up the large gap in these deep blue states.
More promising are those with smaller populations, or narrower gaps to be overcome in large states. Pennsylvania has 60% turnout, leaving a large number of infrequents available to close the 5-point gap from 2012. Connecticut has roughly 60% turnout, too, and the small population of the state will make it easier to sift through enough infrequents. Nevada has even lower turnout at 56%, the gap was only 6 points, and it's a small population concentrated mostly in the Las Vegas area.
Michigan, with 65% turnout, is only somewhat less favorable than those three, and much more favorable than the Lutheran Triangle states (MN, WI, IA).
The swing states also have only somewhat higher-than-average turnout, in the low-to-mid 60's, including Ohio, Florida, North Carolina, and Virginia. These states have smaller gaps to close, and don't need to rely on the infrequents like the more solid blue states do, but certainly a boost among infrequent voters here would make them comfortable wins rather than the typical squeezing blood from a stone for Republican candidates.
Finally, there are two blue states with very few infrequents to mobilize for the first time, but that still seem to be switching to Trump based on the frequent voters re-aligning -- Iowa and New Hampshire, both with turnout of 70%.
And of course the re-alignment of frequent voters in Rust Belt states could flip some of the other blue states, like Pennsylvania and Michigan. But that's a separate topic.
The following states ought to be ruled out, based on high turnout preventing a surge among infrequent voters, and the existing voters being mostly against the Trump movement, so that re-alignment among them is not likely -- Colorado, Minnesota, and Wisconsin, none of which Trump won even in the primary stage.
As we continue this series on a potential surge of usually hidden voters, we'll discuss what signs to look for between now and the election to see if there is in fact a whole bunch of infrequent voters coming out of the woodwork. For now, at least we know where to restrict our focus -- and where to ignore, even if there were solid evidence, like the red states that we've already got, with or without a surge in turnout.