Perfect disproof
The zombie abdication of "Trump", allowing Hillary to occupy his body, provides the FINAL AND DISPOSITIVE DISPROOF of 1787.
If we had kept the NATURAL Parliament instead of inventing a new shit-filled system based on evil atheist anti-scientific dystheories, a prime minister who suddenly abandoned his own agenda would be KICKED OUT FAST. His office would depend on the majority in Parliament. A majority elected on a Populist platform would yank the traitor off the platform and replace him with a more reliable delegate.
This doesn't happen often in countries that retain Parliament, but it does happen
when necessary. It happened in Britain last year, and in Australia the year before. The PM got sloppy or turned out to be weak or fake, so the party that elevated him was able to de-elevate him QUICKLY.