Politicians may be ambitious, promiscuous, worm-ridden sociopaths, but I don't doubt that most of them, when they first decide to run for office, are genuine in their conviction that they can help society become better; right wrongs, foster happiness, stand up for justice - the whole inspiring conference speech. They have a vision of what they want society to be and it tends to be Eutopia.
The right often feels nostalgia for a time that never really existed: in England, it could be for a time of Victorian gentlemen flattering Elizabethan ladies with Edwardian prose and medieval chivalry, or for some fictitious country village where everybody knows everyone's names and the home fires are always burning and brandy greets good tempered farmers after a hard day's honest toil. In America, it is some 1950's suburban paradise, where father knows best and little Jimmy with his rosy red cheeks plays hopscotch on the sidewalk while mom bakes a pie. Islamic fundamentalists are in a swoon over some non-existent golden age of Islam, where Shariah was uniformly followed by all Arabs everywhere exactly the same way.
All these nostalgic visions are heavily edited, of course: the insidious evil inherent in every one of them never rears its head in the conscious minds of Conservative and Republican alike.
However, in their nightmares they must see the slavery, the racism, the oppression, the violent subjugation of a good portion of the world that made this past possible. Victorian gentlemen might flatter their ladies, but they'd strangle their whores just to hear them squeal and beat their coolies afterwards for sport; the farmer may have toiled, but he also mechanised, so large swathes of the countryside could be worked by a solitary man, leaving the village's labourers out of luck; father's word was law, so his wife darn't whisper a word about her black eyes and little Jimmy knew to stay away from those Clay boys: they were hated by God and cursed with black skin. The Taliban forget just how accommodating Muhammad and every successful Islamic ruler was to other faiths and cultures, but they follow the Kuran to the letter; you don't expect them to READ it too, do you?
The dreams of the left are no easier. Their Eutopia is a land not yet realised, a land of the future; for the communist, it is an egalitarian paradise where workers enjoy an equal share of the fruits of their labour, for the socialist fairness is a meritocracy where one works more, produces more and so gets more, regardless of rank within society or company. Money is abolished entirely, of course (hurray!); everyone just follows the rules because the rules are good for everyone.
That is the starry-eyed vision of those little Lenins you see peddling 'Socialist Worker' on UK campuses. The more practical among them acknowledge the necessity for governance and so advocate a central bureaucracy as the solution and suddenly, through that chink of practicality, comes flooding the light of history with its gulags and its polit bureau, its KGB, Pol Pot and The Great Leap Forward. Our starry-eyed Lenin is blind to all that, he sends us onward into his shadow - Eutopia is always ahead.
The left, however, is not limited to the reds. One also finds theories on reformations of society through technology like in Star Trek (oh, yes; it's a political philosophy) where somehow the ability to travel to other planets stops humans from being greedy and violent (???). The idea that mankind could outgrow his basic desire to dominate and destroy is touching and inspiring, as is the idea of a world where everyone works for the betterment of themselves and society and lives harmoniously with nature. Pandas should be fed; criminals reformed, not punished; races should coexist harmoniously; sex should be a free expression of joy and love, not a power game or a shameful fumbling.
The left is good at mapping Eutopia in the privacy of its own delusions, but when it comes to the route to Eutopia, the way is somewhat less clear. In the past it always seems to have meant millions of people dying through starvation and mad experiments in production, hence the lack of discourse about socialist Eutopias come election time.
I can see it now, the honest politician stands up at his party's conference; "About a tenth of the electorate will be starved to death in order that we can watch our woolly policy of wealth redistribution and social restructuring fail. Then we'll hush it up and declare everything a roaring success, before I kill most of my competition for post of Supreme High Chairman, and rule for thirty years as a paranoid, irrational, cold psychopath, unable to look myself in the mirror without involuntarily vomiting."
Of course, exceptions abound to the rule - hippies who want to shed all technology and live butt naked in the trees are nostalgic for a fictitious past, but are certainly on the left - however, it works as a general rule that the right is nostalgic for a fictitious history and the left dreams of an impossible future.