Around 31% of Americans are working class. This group includes those in waged labour, especially in manual labour, manufacturing and industrial sectors. Deindustrialisation in the second half of last century created structural unemployment in sectors including these, and led to the formation of the Rust Belt area in the US. This region faced industrial decline due to international competition in manufacturing.
Trump promised to renegotiate trade deals and bring back manufacturing jobs in the declining industrial and post-industrial areas to appeal to the American working class. Working class Americans who were left behind by innovation and technological change felt listened to.
Most of Trump's voters in 2016 were not actually working class. Approximately a third of the Trump electorate had household incomes below the US median income, roughly a third earned between $50,000 and $100,000 (around 43,825 - 87,650 euro), and one third earned more than $100,000. Hillary Clinton actually received more votes from working-class Americans in 2016 than Donald Trump, a result indicating that working-class voting patterns that tend to favor Democrats over Republicans.