Forget about the e-mails and the tweets. Trade between nations has become a vital issue during this year’s presidential campaign as Hillary Clinton and Donald Trump look for an advantage among voters.

Automakers, meanwhile, are struggling to stake out a position in the debate that both defends their position under the North American Free Trade Agreement and criticizes the proposed Trans-Pacific Partnership, a sweeping trade agreement with nations in the Pacific Rim region where the U.S. is trying to maintain influence.

At the same time, trade unions such as the United Auto Workers and United Steelworkers,  which for four decades  have criticized U.S. trade policies as job-killers, are scrambling to persuade members not to listen to Republican nominee Trump, who has developed a strong following among blue-collar voters.

Trump has made attacks on American trade practices one of the pillars of his yearlong quest for the White House. He unleashed a blistering attack on the notion of free trade during a recent visit to western Pennsylvania, where he also vowed to impose tariffs on foreign-made products, including new vehicles and auto parts.

Western Pennsylvania and neighboring eastern Ohio are heavily industrialized and have large numbers of white blue-collar voters in places such as Warren and Lordstown, OH, as well as around Pittsburgh. They have been skeptical of both Republican and Democratic candidates over the years.

Trump wooed those voters in a campaign statement: “Hillary Clinton is the enemy of working people and is the best friend Wall Street ever had. I will fight harder for American workers than anyone ever has.”