While researching the map I intend to make for the 2022 midterms in the House I looked into the current breakdown of the House by its caucuses. For the unfamiliar, the US Government is divided into 2 parties, the Democrats and Republicans, but those parties are themselves divided into caucuses. Some are bipartisan and/or represent members of the House who back a single issue, or an underserved minority community, etc. BUT there are 6 big ones that are functionally political parties in their own right.
House Freedom Caucus - The Extreme Right successors to the Tea Party. These guys have members who think Trump isn't conservative enough, but otherwise back Trumpism without question.
Republicans Study Committee - Founded in 1973, the RSC is the core of the modern Conservative/Reaganite Republican Party. They are by far the largest of the 6 main caucuses and control House Republicans with 158/209 seats. While the Freedom Caucus is the nominal extreme-right caucus of the House, the RSC has drifted further to the right and taken more and more control of the House Republicans.
Tuesday Group - While there is no longer any formal caucus for Moderate Republicans in the House, until 2019 and 2020 moderates were members of the Republican Governance Group or the Main Street Caucus, both of which have been dissolved. That said, mainly of their members remain in Congress and at least 44 House Republicans identify as part of the group.
Blue Dog Coalition - Once one of the larger caucuses in the Democratic Party, the Blue Dogs have steadily declined to being the smallest ideological caucus. Made up of 19 conservative Democrats, the caucus is functionally the home for Democrats elected in Congressional Districts that used to primarily elect Republicans.
New Democrat Coalition - The largest single coalition in the Democratic Party, and until 2018, decidedly the leaders of the House Democrats. At least 8 Democrats are not registered with any caucus, but they're represented here as members of the NDC for convenience sake. The NDC is the home to centrist/moderate/Clinton Democrats, and has dominated the party since the 1980s. Today they are in a power-sharing relationship with the next caucus...
Congressional Progressive Caucus - Founded by Bernie Sanders and Nancy Pelosi (among others) in 1991, the CPC has slowly drifted further to the left and become more ideologically unified. While many members of the NDC were and still are members of the CPC as well, it has gradually purged the NDC from its ranks (Pelosi left in 2003). It is chaired by Pramila Jayapal, Katie Porter, and its Whip is Ilhan Omar, and as of 2022 has 99 voting members in the House, 4 more than the NDC. In 2018 the Caucus deprived the NDC of a majority in the House Democratic Caucus, leading to the challenge for Pelosi's speakership, and the subsequent deal for CPC member Hakeem Jeffries to take over as party leader after 2022. Many people mistakenly think the progressive movement is only represented by "the Squad," but they were not the only young progressives to win elections in 2018 and 2020. And while AOC won in a district that leans Democratic by 25 points, seven won seats with a lean of 5 points or less, and three won seats in Republican leaning districts.