If this summer in politics had a singular and omnipresent theme, it would be Donald Trump. Trump has survived public statements and controversies that likely would have have ended other candidacies. Trump is on the cover of magazines that will define the times for future generations. Trump is at the top of most polls.

And, as summer draws to an end, GOP officials now seem resigned to a certain fate: One way or another, Trump will be a factor in the 2016 race -- a factor that must be managed and/or dealt with.

For the party, this involves harnessing the political enthusiasm of Trump's mostly but not exclusively white supporters -- people attracted to Trump's hard-line immigration and trade platforms -- and yet somehow broadening the party's appeal beyond it's overwhelmingly white base. Both are pretty essential to the GOP's path to the White House. The truth is, fears are well-founded that Trump's supporters, many of whom are also known to be infrequent and inconsistent voters, will simply sit the election out if Trump is nowhere near the GOP's center stage.

In fact, white voter participation -- meaning the actual share of those who turn out and vote in presidential and congressional elections -- has been declining since about the mid-2000s. And in 2012, that pattern produced a first: African Americans participated in the presidential election at the highest rate, and white voters lagged behind in second place.

Consider these long-range looks at voter turn out in presidential (Chart No. 1) and midterm (Chart No. 2) elections.

Take a close look at both of those charts. The slow but clear decline in white voter turnout in both presidential and congressional elections started long before Trump joined the presidential race. The decline predates Obama's White House run and certainly his presidency. And while black and Latino voters haven't sustained the pattern of slow and steady increases in midterm elections, the top chart tells us that blacks and Asians have done just that in presidential election years.

Look closely: Something is eating white voters and has been for years.

This begins to explain why, in the 2016 GOP primary season, a collection of men and one woman who have never held public office -- businessman and reality TV star Donald Trump, retired neurosurgeon Ben Carson and former tech executive Carly Fiorina -- are outperforming more conventional candidates with more campaign resources. It's early, of course, but that pattern sure is clear and intriguing.

One part,  at the very least, of Trump's appeal to the GOP's largely white voter base has been his immigration policies. That includes the unilateral deportation of an estimated 11.3 million illegal immigrants and at least some of their 4.5 million U.S.-born children.

Trump often turns to generalizations about immigrants, entire countries -- namely China and Mexico -- and people who just happen to bear some loose resemblance to long-running stereotypes and ethnicity-enhanced suspicions. And the consistent way in which Trump supporters report admiration for his unbridled, politically incorrect way of speaking suggests that there might be some level of racial anxiety fueling support for his campaign.

To be clear: No one is saying that's the only reason that voters like Trump, or that this is the sole reason that white voters like Trump. But that is part of the appeal for some of his supporters.

In the crowded Republican field, the candidate who can figure out the Trump Secret Sauce might have a shot at attracting some of Trump's supporters if and when Trump is out. And the many other men and women competing to become the GOP nominee know this.

Sen. Ted Cruz (R-Tex.) has gone so far as to plan joint events with Trump. And both former Florida governor Jeb Bush and Wisconsin Gov. Scott Walker have experimented with embracing harder-line immigration ideas and language. Those experiments have registered as pretty awkward, if not outright shoddy moments in both campaigns. In fairness to both Bush and Walker, of course, Trump has had years of practice speaking about himself and others in superlative terms, lobbing insults and generalizations at entire groups and living with the consequences.

But solving the riddle of the disappearing white voter is, for every GOP contender, critical. And yes, it's even more critical for Republicans in 2016 than Democrats. (Remember those charts above.) White voters comprise the vast majority of the GOP base. Broadening the party's appeal is an unavoidable long-term goal, but attracting as many white voters as possible to the polls is an immediate imperative.

Now, if all this business about white voters and black voters, Latino voters and Asian voters just plain disconcerts you, welcome to the present and future.

As the nation's population hurtles toward a state in which minority groups collectively comprise the country's majority (that will happen in 2044, according to the most recent Census projection) every feature of group political behavior -- meaning the well-documented ways in which black, Latino and Asian and, yes, white Americans behave politically -- is going to be increasingly important.

Sure, individual voters of all races and ethnicities sometimes operate in ways that are not like other members of their group. And other factors like income, education and geography also influence voter behavior. But race and ethnicity are major factors. Dismiss that and you won't be able to understand politics -- much less succeed in them -- in just a few years. In fact, you might have missed some significant aspects of national politics since Richard Nixon was in the White House.

That's why inside both major political parties, knitting together and sustaining cross-racial coalitions of voters is a constant topic of conversation, debate and sometimes controversy. But the work of putting that in action is not simple. It, too, requires political muscles that some candidates have yet to develop.

Case-in-point: Scott Walker's comments in this next CNBC interview.

Walker doesn't just avoid the question of what he, a politician who has always won Wisconsin-wide elections with a nearly all-white voter base, will do to broaden his appeal. He says something that those Trump voters who feel that they are overlooked and ignored by the "political class" probably won't like much.

"The nation as a whole is not going to elect the next president," Walker said. "Twelve states are, and Wisconsin is one of them right now. New Hampshire [too]."

Translation: People who live in the remaining 38 don't matter.

What Donald Trump is doing on the campaign trail

U.S. Republican presidential nominee Donald Trump speaks at a campaign event at Trump Doral golf course in Miami, Florida, U.S. July 27, 2016. REUTERS/Carlo Allegri (Carlo Allegri/Reuters)