Trump's border speech could have been worse -- it could have said no barrier whatsoever, and btw we're amnestying everybody. But it failed to realign the GOP, adhering to the Reaganite orthodoxy about waging a war on crime and drugs in order to distract from the elite sources of our deteriorating standard of living and fragmentation of our communities.
In particular, he failed to name and blame the enemy -- the elites on the GOP side, who have been steering our society since the 1980s, and who have a collective material interest in cheap labor. Their sectors of economic activity are physical and labor-intensive, unlike the informational and non-labor-intensive sectors who control the Democrat party. The cost of labor is a major component of the cost structure for GOP elite sectors like armed force (military, police, prisons), manufacturing, agriculture, and energy.
Their cartels will always push for cheaper labor in order to maximize profits, and when they organize together in a political coalition like the GOP, they will pursue this goal through replacing American workers with cheap foreigners. Either by re-locating the worksite to the cheap labor colony (manufacturers who off-shore their factories), or by bringing the cheap labor here if the worksite cannot be re-located (agribusiness whose worksites are its immovable land).
Democrats have been the powerless shut-out opposition party during the Reagan era, so they deserve less or no blame in general. On immigration, they have not passed the amnesties or open-borders laws that Reagan and Bush Sr did, and that Bush Jr spent his entire time attempting. Workers -- not the elites -- in labor-intensive sectors are a major chunk of their electoral base, especially those who are collectively organized, like union members.
Even their elites do not depend on slashing labor costs because that is just a rounding error in their cost structure. For example, the senior cartel of their coalition -- finance -- employs nobody, and is still at the top of their industry on a global scale. Their "costs" are when they take financial risks that blow up, like lending someone money who doesn't pay it back. Those are balanced by the rewards when their risks pan out, like when the debtor does something highly profitable with their loan, and manages to pay back the loan plus interest. Finance may seek bailouts if their bets don't work out, but they do not seek cheaper labor.
So far, Bernie Sanders has been the only major politician to call out these cheap-labor material motives as the basis for our immigration policies, casting blame correctly on the GOP elites. During the most recent presidential election cycle, he dismissed "open borders" as "a Koch Brothers proposal". He represents the electoral base of the Democrats -- actual or potential union members -- but his view could be harmonized with the elites of his party like the Wall Street investment banks, whose bottom lines would not be affected one way or the other if we closed the borders.
During his 2016 campaign, Trump railed against the GOP elites, though not so much on immigration as for trade / industrial policy and foreign policy. Still, he was not blindly partisan in his blame, and delighted in antagonizing the party's elites, who he said were manipulating the other candidates like puppets on a string. Now in office, Trump only blames the powerless opposition party, rather than returning to his campaign trail slogan of being even more disappointed in the Republicans than in the Democrats.
Aside from having the wrong analysis, and therefore the wrong proposed solution (hector Congressional Democrats), this speech took the wrong move in building a broad coalition to support the supposed goal of reducing immigration. By being partisan, he turned off all Democrats and most Independents -- who want to hear both parties blamed -- and by focusing on the themes of crime and drugs, he appealed only to conservative morality, giving liberals and moderates an easy excuse not to join him.
Focusing on matters of class and economics, and populism against elitism, would have had greater success in building a coalition at the popular level, but also at the elite level. Now, he has no elite support, including from Republicans, whose material interests militate in favor of cheap labor, and therefore open borders. If he had opened the door for Democrat elites, such as finance, they could have amassed political capital for appearing to be the good elites, as opposed to the bad elites, on the economic concerns of the working and middle classes -- while not having to sacrifice their own material interests. That's how the borders stayed closed during the prosperous New Deal era, when finance still controlled the Democrats but they were the dominant rather than opposition party.
In order for the Democrats to re-gain dominant-party status, they require massive defections at the electoral level, as well as one or more elite sectors.
As for the latter, that is a separate post, but it is industrial commodities like steel, whose elites have generally supported the GOP but who have been wiped out by the de-industrial trend pursued by the more powerful manufacturers of finished goods, who want cheap materials as well as cheap labor, and who have been only too happy to substitute foreign for American steel. Robust protection of steel would secure Pennsylvania back for the Dems, while mealymouthed marketeering would give them little reason to return.
As for popular support, they need anyone who feels like the GOP has sold them out. These are people opposed to wasting resources on maintaining our crumbling and pathetic empire abroad. They are people who want to re-industrialize the economy, in order to raise the average person's prosperity back to industrial-society standards rather than continuing to revert to pre-industrial peasant levels. And they are people who want to dramatically reduce the share of the population who are foreigners.
The GOP during the Reagan era has sold out all of those groups, and they feel like they "want their country back". A minority do not really mean this, and are dyed-in-the-wool Reaganites who are simply upset that their gains also come with some costs. But most disaffected non-Democrats really do want to go back to the New Deal era, which did include closed borders, a more homogeneous population, and civil rights focused on one group, the descendants of African slaves, who were deeply rooted in this country and had been mistreated, rather than diluting civil rights into "every fresh-off-the-boat minority group gets to be represented in Disney movies".
Realigners on the Democrat side do not have to make explicit nationalist appeals to the very large group who "wants their country back," but rationalizations are not important, the outcomes are. As long as that group can see that immigration will come down, and the population will be more native-born, they don't care what the reasoning is, what the public rhetoric is, or what party or politician gives it to them. If it's a democratic socialist like Bernie Sanders, and if he's making purely class-based rather than nationality-based appeals, who cares? That's just PR.
There would be a wave of people who have "never voted Democrat in my life," or who have done so only occasionally and grudgingly, who will now do so eagerly and devotedly. That will mark a departure from the Obama coalition, most of whose GOP defectors were temporary and grudging -- and who went right back to the Tea Party and neutered Obama from getting anything done.
The right must move in that direction also, giving relatively less importance to nationalist appeals in the context of immigration, and more to economic appeals. Breitbart, Ann Coulter, and Tucker Carlson are leading the way on this shift in appeal. They are positioning to be the opposition party under a Bernie-dominant era -- agreeing on the big-picture fundamentals, in the same way today's Democrats share the GOP's neoliberal orthodoxy, but are more culturally liberal. The new GOP will be culturally conservative sympathizers of the Bernie / Ali O-C agenda.
And the left must accept these new populist Republicans, as a preferable opposition compared to one dominated by Reagan, the Bushes, McCain, Romney, Ryan, et al. At the outset of the realignment, they will even have to tolerate them in the Bernie coalition, in order to give it the oopmh necessary to overcome all the obstacles in its way and secure status as the new way of doing things. After that initial hurdle has been cleared, then the conservative populists can separate off on their own, into a new populist GOP.
That will be no different from everybody voting for Reagan, to terminate the New Deal, before segregating into red and blue Reaganite states. Or everyone voting for FDR, to secure the New Deal, before segregating into red and blue Midcentury states.
The alternative is to favor "woke neoliberals" over "racist populists," i.e. prioritize identity over class, and deliver an even more crippling level of inequality and immiseration than the Reaganites. There are only a handful of woke populists, not enough to sustain a dominant-party coalition. They will have to choose which slate of issues is more important in the trade-off, and that will determine whether we head toward another New Deal or another Robber Baron era.