Even when circumstances do change, it's not clear that the government may renege on such a pledge. Wilson was returned in 1916 on a pledge to keep the USA out of WW1. Less than a year later, in changed circumstances, he took the USA into the war, with overwhelming support of the population. Had he held a referendum, it is clear that it would have passed. Should he have held one? I think he should have, but let Mackenzie King have his say:
When those who hold representative and responsible positions have given a definite promise to the people, they have created an obligation to act in accordance with that promise, until the people are again consulted. Such an obligation may not be binding according to law, but as an obligation it is no less sacred.It should be noted that, even after the referendum passed with 64% of the vote, releasing the government from its promise never to send conscripts overseas, conscription was not introduced until 2½ years later, and even then only after a political crisis.
There are those, I know, who make light of what they call "political promises." It will, I think, be generally agreed that a political platform or programme is one thing; a definite and concrete promise or pledge is quite another. Because of circumstances, a government may, without breaking faith, fail to carry out, to the letter, its full programme. No change in circumstances could, however, justify a government in ignoring a specific pledge to the people, unless it was clear that the safety of the nation was immediately involved, and there was no possibility of consulting the people.
The dictator Sharon is obviously cut from a different cloth.