system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why can't politicians be contractually obligated to fulfill their basic campaign promises?
gpt
Other than the obvious "it's impossible" or "they cannot be punished for lying", the simple matter of the fact is, a single politician is merely a voice in the crowd. Sure they have a louder voice than us regular citizens, but it's still a crowd nonetheless.

One can claim to do A while running for office, and when they finally get into office and try to perform A, other people in the congress can be like, no, that's now what we promised our people. Then A is scrapped and the politician is left in the dust. 

For something to happen, the majority must agree. That means if the person running for office wants to fulfill his campaign promises, he must make campaign promises that the majority of the congress will agree upon. But the reason why people are voting up new congress members is for change. If you're presenting ideas that are agreeable by congress, nobody will vote for you. If you're presenting ideas that are not agreeable by congress, people will vote for you (if that's what the people want).

TL;DR: Politician wants to legalize weed, people vote him up, politician promotes weed legalization to congress, gets rejected, campaign promises unfulfilled.