It's usually attributed to Huey or Earl Long both, back in the day, Governor of Louisiana. Presented with the truth about a campaign pledge and after deciding to go back on this promise, the Governor says to his advisor, "tell 'em I lied". It sort of reinforces the public's opinion about what politicians will say to get elected - I'll fix that, stop this, build something, make something. Promises that, like April snow, vanish at the first ray of sunshine.
Seems there's a reason:
We know from public choice theory that lying is more rational for a politician than for individuals in other walks of life. A politician's lies are less likely to be noticed or remembered by the "rationally ignorant" voter. Rational ignorance means that the individual voter has little incentive to invest time and money in gathering and analyzing political information because he will not be able, with his single vote, to change the election result. The politician running for office also has an incentive to lie when deprecating his opponents' character. If he wins, there will be no way to know whether or not his opponents would have been as bad as he claimed. And since the politician has no property rights in his office, the discounted value of his political reputation over time is very low, giving him an incentive to trade long-term credibility for short-run victories.This observation (from a super article by Pierre Lemieux) is compounded by two additional problems. The first is that the voter wants to be lied to, wants to believe that government can solve whatever problems that voter has in his or her life. And as politicians we are only to happy to indulge this delusion by saying "of course, do you want that in green or blue?". The second problem is that truth is, as anyone looking at 'fact check' websites will know, often a matter of degree or emphasis. There's a lot of shouting about 'post-truth' and 'fake news' but this anger is limited - it doesn't touch on things that aren't true but that the public really believes are true. Here's Tim Worstall:
Perhaps a red flashing cop light beside an article which contains any of the following lies?What? You think these things are true? You read angst-ridden articles about them in the Guardian? Us politicians lie because you think things like imports being bad and exports good, that 'dumping' steel or solar panels is bad for our economy, and that regulation supports markets.
The minimum wage does not cause job losses.
Corporations should pay more tax.
Global inequality is rising.
US child poverty is over 20%.
We have widespread poverty in the UK.
17% of UK families cannot afford enough food.
If you want truth then the most grown up thing you can do as a voter is to assume that the government is not interested in making your life better, is not concerned about the things that you're concerned about, and has the primary function of sustaining its current size, structure and powers regardless of their actual value to society. And, that politicians lie because you want and expect them to lie.