Likewise, if an economist tries to tell you where the stock market will be in a year, you can safely ignore that. But if he tells you a gas tax holiday is an unambiguously bad idea, that's worth listening to, especially if economists on both sides of the aisle agree.
If you think it is okay to ignore economists because they are so often wrong, you're looking at the wrong questions. Economists are generally wrong with complicated models but right about concepts. For example, they know that additional domestic drilling won't make much of a dent in the energy problem. And they know that free trade is generally good for all economies. (You can argue with my examples, but the point is that some things are generally known by economists while not being understood by the general public.)
By analogy, a mechanic knows that changing your oil is good for your engine, but he can't tell you what problems you will have with your car next year. You shouldn't ignore the mechanic's advice on changing oil just because he doesn't know when your battery will die, or because he didn't personally perform any scientific studies on oil changes.
Doctors are often wrong, but you are still better off going to the doctor than diagnosing problems yourself. And when you get the opinions of several doctors, your odds improve, even if those several doctors aren't a scientific sample. The important thing is that following a doctor's advice, or the consensus of several doctors, increases your odds compared to the alternative. And the more doctors the better.
Some of you noted that the candidates have top economists on their payrolls, so voters can be assured any president is getting good advice. But realistically, an economist involved in a political process has to support the candidate's ideas or he's off the team. At best, one of the candidates obviously has bad economists advising him because they disagree with the other guy's economists.
Some of you noted that most economists are Democrats. Prior to doing the survey, I expected it would be the other way around. But indeed, most of the economists we surveyed are registered Democrats. But there are plenty of Republicans and independent voters in the survey so you can see how each group weighs in separately. Personally, I will be most interested in the independent voters and the economists who cross party lines.
After the results are announced I'll tell you how we cleverly found over 500 economists. There's a clear limit to how scientific you can get with your sample when it is a bunch of people who chose economics as a profession and were easily findable. But again, you have that same problem when you pick your doctor, or when you get second opinions. You're not dealing with scientific sampling.
You're going to wonder what my own political bias is. In the interest of full disclosure, I think I registered Independent the last time I voted, but frankly I don't remember. I'm not superstitious, which leads me to be socially liberal. Economically, I'm conservative. I'm closest in philosophy to an Arnold Schwarzenegger Republican. He seems to be interested in keeping the government out of people's private lives and managing things based on data as opposed to faith. Neither presidential candidate floats my boat. One wants to transfer my money to other people and the other is a lukewarm corpse. I think both candidates would be indistinguishable in foreign affairs because their options will be so constrained. Those are my biases.