If we were to pick the "hallmark" year in the demise of representative government in the United States, then 1921 would be that year. A Republican Congress, dominated by rural politicians who stood to lose clout in a quickly urbanizing nation, purposefully failed to reapportion the House following the 1920 census. And having gotten away with acting unconstitutionally, the Republicans compounded the crime in The Reapportionment Act of 1929, such that apportionment of 435 seats would occur automatically following each decennial census. See section 22 of "The Act" (PDF)
The 435 limit creates huge electoral districts, easily gerrymandered in bipartisan manner to "lock up" safe seats. Election outcomes are "engineered" by the parties and many voters simply stay home.
