The Congressional Progressive Caucus (CPC) is a formal membership organization within the United States Congress that represents the progressive wing of the Democratic Party. Founded in 1991 by then-Representative Bernie Sanders (I-VT) and several other House Democrats, the CPC has grown from a small group of about 20 members to become one of the largest ideological caucuses in Congress. The caucus includes voting members of the House and Senate, as well as non-voting delegates from U.S. territories and Washington, D.C. The size of the CPC after a midterm election is a closely watched indicator of the Democratic Party's ideological balance and the influence of progressive policies within the party. The prediction market question focuses on the total count of U.S. Congress members, including non-voting delegates, officially listed as CPC members on February 1, 2027. This date falls after the 2026 midterm elections, which will determine the composition of the 119th Congress (2027-2029). The outcome of these midterms will directly affect the caucus's size, as open seats, retirements, primary challenges, and general election results shift the ideological makeup of the Democratic caucus. The CPC has historically grown during periods of Democratic electoral success, particularly in 2018 and 2020, but has also faced internal debates about membership criteria and ideological purity. Recent developments include the CPC's role in shaping Democratic legislative priorities during the Biden administration, such as the Inflation Reduction Act and the American Rescue Plan. The caucus has also been active in pushing for Medicare for All, the Green New Deal, and student debt cancellation. The 2024 election results will influence the CPC's trajectory, as the party's performance in swing districts and the replacement of retiring members will determine whether progressive candidates gain or lose seats. The caucus's leadership, including current chair Representative Pramila Jayapal (D-WA), has worked to maintain unity while navigating divisions between progressives and moderates. People follow the CPC's size because it signals the direction of the Democratic Party and the likelihood of progressive policy proposals advancing. A larger CPC after the 2026 midterms could indicate growing support for progressive ideas, while a smaller caucus might suggest a shift toward centrism. The prediction market allows participants to bet on this specific outcome, reflecting broader interest in how electoral dynamics shape the ideological composition of Congress.

Historical Context

The Congressional Progressive Caucus was founded in 1991 with 20 members, including Bernie Sanders, then a House member. The caucus grew slowly through the 1990s, reaching about 50 members by the early 2000s. The 2010 midterm elections, which saw a Republican wave, reduced the CPC's size to around 70 members as many progressive Democrats lost their seats. The caucus rebounded after the 2016 election, with the rise of the progressive movement fueled by Sanders's presidential campaign. By 2017, the CPC had about 75 members. The 2018 midterm elections were a turning point: Democrats gained 41 House seats, and many newly elected progressives, including Alexandria Ocasio-Cortez, Ilhan Omar, and Rashida Tlaib, joined the CPC. The caucus's membership swelled to over 90 members by early 2019. The 2020 elections added more progressives, bringing the CPC to over 100 members for the first time in its history. The 2022 midterms saw Democrats perform better than expected, losing only a few seats, and the CPC maintained a size of around 100 members. The caucus has also expanded to include non-voting delegates from D.C., Puerto Rico, Guam, the U.S. Virgin Islands, American Samoa, and the Northern Mariana Islands, who are counted in the total membership. The CPC's growth has been accompanied by internal debates about membership criteria. In 2017, the caucus adopted a rule requiring members to pay dues and attend regular meetings, which led to some members leaving. The caucus has also faced criticism from moderates who argue that its influence pushes the party too far left, potentially costing Democrats seats in swing districts. The 2024 election results will determine the baseline for the 2026 midterms, as the CPC's size depends on the overall Democratic seat count and the ideological composition of the party's candidates.