"... there are many potential audiences in the electorate. Politicians and political parties choose which ones to nurture -- and are fairly held responsible for those choices. "

...................................................................................................................................................................
COMMENTS: 
*  Most of this column I agree with. But the "tribal whites" that Trump is appealing to weren't created by the Republican Party, they've existed all along. It's just that the Republican Party has swept them in, for the simple reason that the party actors' agendas matched their interests better than the agendas of the Democrats. And that faction's grievances aren't imaginary -- The brunt of the losses suffered by the disestablishment of segregation (and the partial reverse discrimination that is affirmative action) are born by less-educated whites; the better-educated whites have been largely insulated (quite possibly because the policies have been instituted by better-educated whites). Similarly the labor competition due to immigration of poor people from Latin America and the opening of trade with China have mostly hurt the same people, while making cheaper services purchased by better-off people.  In my opinion, the problem with Trump supporters is that much of what they want (or need) can't be given. Immigration from Mexico has dramatically slowed in the past few years; it's quite possible that the significance of Spanish in US culture is declining. Manufacturing is becoming more automated, to the point that China is losing manufacturing jobs. Splashy symbolic actions are possible, but it's hard to see how to effectively reverse the economic and social changes of the past few decades.
   *  The Tribal Whites are the targets of the still extant Southern Strategy. Without the voluntary decision of the GOP to appeal to the heirs of Johnny Reb, they would have been stuck in a very weak (George Wallace) American Party and slowly abandoned the idea that racism and other bigotry was worth counting as an important value in political decision making.
*  ... So, here comes Trump.  From what I've read, Trump's voters aren't too concerned about taxes. They're concerned about getting back the status and economic security "tribal whites" have lost - making 'America Great Again'.  Could Trump be their community organizer? Make them talk and realize what it is they need to regain their place at America's table? Make them realize they don't share much in common with the Koch's.  Much has been written about the tribe's "false consciousness". How appeals to working class consciousness fall deaf on Americans ears because each of us can imagine him or herself getting rich, so we unconsciously adopt the political goals of the rich. "Tax the rich" doesn't motivate us ordinary folks - according to this idea.  Maybe Trump can change that? He'd have to modify his message. Like Roosevelt, he'd have to betray his class.
*  this hidden base, who just supposedly came to the fore :}, represent how crazy 'so-called' conservatism has become. Trump represents the fall of the worthless GOP with its always on-going hate, spin and lies. look at the worthless House of Fools, look at the leaders of both congresses!! what has the GOP done the last 6 years but sit on theirasses!!!!  Trumps bullying, his irrational hate through bigotry and racism, IS the Rep party, with its fake religion through its zealotry.
...................................................................................................................................................................
The Republican Party Got the Voters It Deserved
By Jonathan Bernstein, May 25, 2016

My View colleague Megan McArdle thinks people are exaggerating the Republican Party's responsibility for Donald Trump. Blaming the party, she concludes, “is like blaming the weatherman because it’s raining, or an economist for a recession.”

True, most Republican party actors resisted the Trump takeover right up to the point, and in some cases even after, all his nomination opponents dropped out. But the Republican Party nevertheless bears plenty of responsibility for the rise of the reality-show star, and many conservatives have acknowledged shortcomings in the party that Trump exploited. The question is still what exactly paved the way for Trump.

Republicans had encouraged, or at least tolerated, schoolyard taunts and far-fetched conspiracy talk long before Trump's campaign. He started out in Republican presidential politics by accusing the president of not being a U.S citizen, a slur that had been bandied about by many highly visible Republicans. He has now moved on to recycling conspiracy theories from 20 years ago about Hillary Clinton that were promoted at the time by talk-show hosts and Republican members of Congress.

Another part is how Republicans lowered the standards for their politicians. Normally voters might oppose Trump as flat-out unqualified for the job, both by lack of relevant experience and lack of knowledge of government and public affairs. But by giving a megaphone to people like Pat Robertson, Herman Cain, Ben Carson and Carly Fiorina, Republicans showed their voters what counts as a "normal" Republican presidential candidate -- and it isn't all that different from Donald Trump. Republican voters had many well-qualified candidates in 2016, but they had been taught by their party to ignore normal qualifications, and they did so (1).

That same observation can be made about how Republicans have tolerated and promoted bigotry, forging a path for Trump to go even further. McArdle is wrong to say that the Republicans' “Southern strategy” of the Richard Nixon era was only incidentally pitched to bigots. In 1968, Nixon was clearly and deliberately going after pro-segregation voters abandoned by the Democratic Party, a strategy continued (for example) by Lee Atwater in the 1988 presidential race on behalf of George H.W. Bush (2).

Additionally, I don't think McArdle’s explanation of the interaction of political elites and masses is quite correct. She says: “You don’t put ideas in peoples’ heads; they just grow there.” But voters have all sorts of ideas in their heads: conservative, liberal, some of which would make for good policy, some which would not. Most of those ideas -- healthy or toxic -- are relatively loosely held, and many times no candidate or party elicits responses based on those particular views.

The more some ideas are frozen out of politics -- for better or for worse -- the less they thrive “in peoples’ heads." And, more important, only when politicians highlight those ideas do they escape from peoples' heads and become political issues. Yes, neither Trump nor earlier Republican dog-whistlers created the audience they played to. But there are many potential audiences in the electorate. Politicians and political parties choose which ones to nurture -- and are fairly held responsible for those choices. 

1.  Another point several observers have made is that by constantly attacking a party "establishment" and in some cases the Republican Party in general, some conservatives weakened the ability of their party to resist incursions from outside. 
2.  McArdle is right that crime was and is a real issue. The same can be said of immigration or terrorism. But they don't have to be covers for politics that's primarily about sending signals to bigots on race, ethnicity and religion. 
...................................................................................................................................................................