They should definitely be held accountable. If I make promises at my job - it is expected that I make good on them, why shouldn't it be the same for them? Those scumbags are ruining our country without repercussion. I think imprisonment is light in comparison to what they deserve.
Politicians should be encouraged to resent their stances on critical issues during the election process, but imprisoning them for failing to deliver on those promises is ludicrous! Politicians are often prevented from carrying out their promises by the government's system of checks and balances, which is built into the legislative process intentionally. America's founders wanted the passage of legislation to be a challenge. Also, politicians are not Gods - they do not have he power to foresee how everything will work out in the end. Sometimes trial and error is unavoidable, and we often discover the full scope of consequences long after legislation has been passed.
It would be ethically wrong and preposterous to imprison a politician for failing to deliver on his promises. However, politicians that intentionally commit crime or fraud can be imprisoned and fined.
No, politicians should not be imprisoned if they failed to fulfill elections promises, because election promises depend on other people and economic conditions that the politician cannot control. Sometimes, other politicians will not vote for the bill the person wants. Sometimes current events change the landscape that makes the promise impractical. We cannot hold politicians criminally responsible for this.