Question for McCain on Food Prices

Economists for Obama have a question:

Question for McCain: Food Prices, Economists for Obama: While waiting for the South Dakota polls to close and Obama to be declared the nominee, I'm watching McCain's speech. ...

At one point in the speech McCain said, "Sen. Obama supports the tariffs that have led to rising grocery bills for American families." This is wrong on two points. First, Obama doesn't support any such tariffs that I know of, although I imagine someone in the McCain campaign would try to argue (falsely) that Obama's criticism of particular aspects of trade agreements means that he supports food tariffs.

More importantly, no one thinks tariffs are behind the increase in food prices. As Obama noted in an interview a few weeks ago, there are many factors behind the rise in food prices. These include rising oil prices (which affect fertilizer and transport costs), poor harvests this year in a few countries, rising demand in Asia, and the rising demand for biofuels, which has been driven by subsidies in the U.S. and elsewhere. I've read many studies on this topic in recent months, and no one has suggested that food prices in the U.S. have increased because of U.S. tariffs. ...

I'm sure we have some journalists among our readers, and I'm hoping that we manage to inspire them (or anyone else who gets a chance) to ask McCain some pointed questions related to economic policy.

So, here's one: "Experts attribute the rise in food prices to a number of factors, but U.S. tariffs is not among them. You've said [see quote above] that the recent increase we've seen in food prices is due to tariffs. But U.S. tariffs on food and haven't changed. How can unchanged tariffs have caused prices to rise? And which one of your economic advisors told you they have?"