There's an assumption that those supporting political parties must do so on the basis of blindly supporting the entire manifesto. "Collective responsibility" means that there seems to be very little room for anyone to think for themselves and criticise anything about their party of choice, because the "other side" will pounce on any evidence of dissent and bang on about it like schoolkids.
And there's plenty of evidence that the ability to think for oneself and honestly express a contrarian moral viewpoint (aka a maverick) didn't do a lot for the careers of folks like Mo Mowlem, Robin Cook and Frank Field. Or Dr David Kelly.
If we cannot tolerate unvarnished honesty in public life, then we must be forcing once-honest politicians to deny their natures. So it is little wonder that so many of them turn out to be amoral liars and all-round shits, quite incapable of answering a straight question with a straight answer..
Nevertheless, the art of compromise is generally forced by the reality of office, and much of the impossible manifesto melts away like the snow in spring. Those who criticised the now-absent elements are not generally warmly welcomed and told they were right along. (You can be excused almost anything in this life, except being proved right - and boy, I should know.)
All governments seem to end up as disappointments, having been elected on a variety of false promises - especially as now, where our PM was only "nodded through" by around 400 sycophants. At least the losing party doesn't have to deal with the consequence of ANY of its unelected policies (the reason why the LibDems have lasted this long?) .
Overall, democracy as we know it, sucks. It was devised in the days when it took days to get between the cities of the UK, and has not changed noticeably since.
Are we not now sufficiently technologically advanced to have a list of propositons to vote for in regular refernda/plebiscites so that we can explore the best of all parties' and individuals' ideas, and cancel the hare-brained stuff without wasting further time, energy, money..?
The process of running the country could then be delegated to an effective "chief executive" which should ensure we really do the get the best talent. Presently such folks are too horrified by the awful media process to want to play politics. Whatever else happens, we should never again gift the job to a filibustering/gerrymandering old Caledonian fraud, living off a dishonest voting system.