Article V says no state can lose its equal Senate representation without its consent. Wyoming gets two senators. So does California, even though California has 68 times more people. The Constitution locks in this imbalance permanently.
Roger Sherman proposed this entrenchment clause at the Constitutional Convention in 1787, worried that large states would use the amendment process to strip small states of their Senate power. James Madison agreed it would protect small states' sovereignty. Legal scholars debate whether you could amend the Constitution twice—first removing the entrenchment clause, then changing Senate representation—but no one has tried. It's the only constitutional provision explicitly protected from amendment, giving small states permanent veto power over any attempt to make the Senate proportional to population.