Like Ronald Reagan, Donald Trump racked up the support of millions of blue-collar white voters in Midwestern swing states, and like Mr. Reagan, the 45th president is pushing to nail down more blue-collar support to ensure a lasting Republican majority. In doing so, Mr. Trump has championed many issues straight out of organized labor’s wish list — he is pressing manufacturers not to ship jobs overseas, he has promised $1 trillion in infrastructure spending, he has threatened a 35 percent tariff to slow Mexican imports and he has vowed to overhaul Nafta.