'When they don't win, they insist on changing the rules'

Among the biggest issues they cite are the amendment process (which makes changes virtually impossible), excessive veto points, the Electoral College, lifetime appointments for Supreme Court justices, a first-past-the-post (winner-take-all) electoral system (rather than, say, proportional representation), and a grossly disproportionate Senate that ensures greater power for the mostly white, more rural small states at the expense of larger ones.
Translation: "This prevents us from changing everything in moments of emotion, and lets those hicks in rural areas- especially the mostly-white ones(we've got to throw race into this)- have a real say instead of being forced to obey us!"

Those things, especially the amendment process, were made that way so it would require deliberation and convincing a good majority of citizens to make an amendment.  The number of Senators per state so that large states, who'd already have a greater number of Representatives, couldn't dominate smaller states.  It works, and they hate that.

They really are the enemy.