Key
In government
External support
Opposition
Ribbon height:
10
50
120
240 seats
Thin line: organisational lifespan; a tick at its end means the end date is not documented. Thick line without a ribbon: the party sat inside another party's club. Dotted verticals: Sejm elections.
Seats are exact for clubs; a club's seats are attributed to its lead party (e.g. Solidarna Polska and Porozumienie MPs inside the PiS-led ZP club count as PiS). 1997–2026 from Sejm API roll calls; 1989–97 reconstructed from the Sejm archive and Wikipedia. Government status from cabinet composition (Mazowiecki cabinet incl. PZPR).