Barack Obama and John McCain are busy demonstrating that in close elections during tough economic times, candidates for president can be economically illiterate and irresponsibly populist.

In Raleigh, N.C., last week, Sen. Obama promised, "I'll make oil companies like Exxon pay a tax on their windfall profits, and we'll use the money to help families pay for their skyrocketing energy costs and other bills."

Set aside for a minute that Jimmy Carter passed a "windfall profits tax" to devastating effect, putting American oil companies at a competitive disadvantage to foreign competitors, virtually ending domestic energy exploration, and making the U.S. more dependent on foreign sources of oil and gas.

Instead ask this: Why should we stop with oil companies? They make about 8.3 cents in gross profit per dollar of sales. Why doesn't Mr. Obama slap a windfall profits tax on sectors of the economy that have fatter margins? Electronics make 14.5 cents per dollar and computer equipment makers take in 13.7 cents per dollar, according to the Census Bureau. Microsoft's margin is 27.5 cents per dollar of sales. Call out Mr. Obama's Windfall Profits Police!

It's not the profit margin, but the total number of dollars earned that is the problem, Mr. Obama might say. But if that were the case, why isn't he targeting other industries? Oil and gas companies made $86.5 billion in profits last year. At the same time, the financial services industry took in $498.5 billion in profits, the retail industry walked away with $137.5 billion, and information technology companies made off with $103.4 billion. What kind of special outrage does Mr. Obama have for these companies?