Institutional Revolution Party. Ruled Mexico for decades - the current President there is the first non PRI president is an extremely long time. The two-party system stinks, but nowhere near the way a one-party system does.
Anyway, in the name of that party, "Institutional" modifies "Revolution". The goal implied in the name is revolution as an institution, not revolution (reform) of institutions.
Revolution as an institution is a pretty horrifying idea - revolution without end, without a goal. And yet, that's really what the U.S. founding fathers knew was required. Our system of elections is supposed to be a perpetual revolution.