Which of the two main parties has failed it's own constituents the most?

I would say the GOP.

They rarely do any of the things they campaign on.

example - they campaign heavily on social wedge issues and "family values" then when they get into office they focus on financial issues... generally ones that benefit the wealthy over the middle class.

Its not the Democrats. The Right refuses to help this country. Go there and blame.

Republican. gift just keep getting bigger and bigger regardless of which party is in

WMDs in Iraq.