It is undeniably true that U.S. labor and trade unions are firmly in the pocket of liberal Democrats. The AFLCIO may as well be the Brown Shirts to President Obama's Fourth Reich. (Yes, I know a Nazi analogy is a little over the top, but they were the National Socialists after all.) On principle, I am very pro-union. I am, after all, a union member. Granted, I don't see how backing Democrats at the federal level has helped us teachers. Ted Kennedy proposed No Child Left Behind in the Senate, and President Obama pushed for more and more state-level controls on local school districts. In fact, it has been Republicans who have loosened federal requirements for standardized testing, something Democrats failed to even consider when they held the legislative and executive branches during Obama's early years in office.
At the state level, at least here in Indiana, the Democrats seem to be very much in the teachers' corner, so funding their campaigns is a good investment. After all, the charter corporations are funding Republicans and have secured massive concessions. For example, charter and private schools here do not have to take the same accountability tests as the public schools; they are free to choose their own. Moreover, they do not receive letter-grade rankings. In the past, public schools outperformed charter schools by so much that in the list of state rankings, public schools crowded the top and most of the bottom of the list were charters. Apparently, this embarrassed Mike Pence and the legislature's bank-rollers and so charters were exempted from accountability.
Industrial trade unions, on the other hand, have been seriously injured by Democrat fiscal and social policy. We have the highest corporate tax rate in the industrialized world. Businesses are fleeing and have been doing so for quite some time. Our environmental over-regulation makes doing business in the U.S. risky and difficult. In recent years, for example, Gov. Jerry Brown's requirement that factories and other large-scale places of business replace their heating and air-conditioning units to a new and expensive "environmentally friendly" model have driven businesses out of California faster than a gassy husband can drive his wife out of the living room. (Don't ask me where I got that analogy.)
Union members would benefit greatly by a more pro-business government. They would benefit greatly by better enforcement of immigration law and better control of the border with Mexico. Let's face the facts--we don't have a flood of Canadians taking jobs away from American citizens (unless you count the entertainment industry, but they don't seem to mind). If you have a scrape on your knee and a gushing artery somewhere else, you focus on the artery. Focusing on immigration through Mexico isn't racist; it's common sense.
However, U.S. labor unions are about to engage in a vast effort to convince their members to vote for Hillary Clinton. They will demonize Donald Trump for past trade deals. They will engage in rabidly ad hominem attacks that completely ignore the issues Trump is raising. If Ted Cruz is the nominee, they will do the same to him even though he also pledges to control immigration and limit illegal competition in the labor market. You can find a great article about this here in The Guardian.
Communism has never produced a thriving economy. Socialism has only produced the illusion of stability supported by crippling debt. Union members (not necessarily their leadership) want jobs and fair competition for them. The Republican agenda will bring us closer to those goals. In this case, politics trumps self-interest for the AFLCIO and its fellow-travelers.