President Biden has never exactly been a liberal Democrat or a conservative Democrat. He has instead stayed in his party’s mainstream. When the party moved right in the 1990s, he moved with it. When it moved left in the 2010s, so did he.

But Biden has not simply gone with the Democratic flow. Over his more than 50 years in politics, he has periodically shown strong opinions about how his party should change — and helped it do so.

Last night in Chicago, Biden took a big step in his long political goodbye, delivering a 52-minute speech at the Democratic convention. In today’s newsletter, I’ll examine how Biden’s presidency shaped his party — and consider whether Kamala Harris is likely to continue these shifts. I think three points are key.

Biden has always understood the class resentments that many Americans feel. (If you haven’t read Robert Draper’s profile of Biden for The Times Magazine, I recommend it, including the section in which Biden analyzes George W. Bush.)

Biden’s political career began in 1972, when he defeated an incumbent Republican senator in Delaware even as Richard Nixon won a landslide. Biden ran as a subtly different kind of Democrat, with a more working-class image than the party’s presidential nominee that year, George McGovern. Biden simultaneously distanced himself from the liberal fervor of the 1960s and portrayed himself as an economic populist. He criticized both draft dodgers and “millionaires who don’t pay any taxes at all.”

Five decades later, Biden became the most populist Democratic president in modern times. This positioning wasn’t just about his background, either. Populism has recently gained a new appeal, thanks to the failure of the market-based economic policies of the past half-century — which are often known as neoliberalism — to deliver broad-based prosperity.