Derogatory term for people who behave exactly like Trump supporters but who are instead aligned with the Democratic Party. Most often used by leftists to describe liberals on Twitter who frequently express their hatred of Bernie Sanders and anyone to the left of him.

When you eat dirt for the first time and leave your family to build a shack in the woods

A derogatory term for a US citizen who usually votes with the Democratic Party, but behaves and believes almost exactly like most supporters of former US President Donald J. Trump.

It is a play on the phrase MAGA (Make America Great Again), the often-used slogan of Donald Trump's campaign and presidency.

People that can be described as "Blue MAGA" are frequently white, upper-middle class, live in the suburbs, and often treat politics as a team sport. They are every bit as racist, classist, sexist, anti-semitic, homophobic, and ableist as the average MAGA supporter, but are just better at hiding it. They frequently support or excuse war, tax cuts for the wealthy, mass incarceration, cuts to the social safety net, Wall St deregulation, and expansion of the surveillance state, if such things happen when a Democrat is president.

Fascist shitlibs who support voter suppression and love candidates who handle rape accusations like scumbags.

An American liberal whose support for Joe Biden, the Democratic Party, or other liberal figures mirrors the emotional fervor of Donald Trump supporters. This typically involves lionizing political figures as larger-than-life and saintly, buying political merchandise, and generally treating politics more akin to a sports team or cultural lifestyle.
A portmanteau of "blue" (the color most frequently associated with Democrats) and "MAGA" (Make America Great Again, Donald Trump's 2016 election slogan).
A more conspiratorially-minded Blue MAGA would be called a BlueAnon (Blue + QAnon).