In political science, one of the lesser known, but not that uncommon, bits of middle ground between a true multiparty political system and a one party state is a "dominant party system."
In a dominant party system, there is more than one legally recognized political party and it even wins minor individual political races now and then, but a "dominant party" always wins in a long standing pattern that persists for decades.
Three of the most common examples are the Democratic party in the American "Solid South" from the end of Reconstruction (after the U.S. Civil War) through the 1950s, and PRI in Mexico for a roughly eighty year period, and the LDP in Japan from the establishment of an representative democracy after World War II until quite recently.
Each of those examples of dominant party systems ended. Starting in the 1960s, the "Solid South" was supplanted by a competive Republican party (at least in federal elections), along with "Dixiecrats" and more liberal Democrats. The main opposition party to the PRI took control in Mexico. And, the LDP stumbled in the face of competition from an upstart party to the left of them in Japan (the "Liberal Democratic" party in Japan is actually its more conservative major political party).
But, political realignment seems to have almost run its course in the American South, threatening to make the Republican Party a reincarnated dominant party of the region with a new name. And, this fall, both the PRI in Mexico and the LDP in Japan have been resoundingly restored to power by voters.
Of course, any viable two party system assumes that there will be some alternation of political power at new elections. The conventional wisdom is that once a dominant party system lapses for a bit that the political system in question is no longer a dominant party system. But, what if we are instead seeing a "relapse" in to long term dominant party systems in three regions that have been long accustomed to operating that way with only recent and brief interruptions. Does that bode ill for the political future of the places that are experiencing it?