We had an interesting discussion about presidential candidates' stances on trade before my 11:00 AM class yesterday. Trade is an issue that definitely cuts across economists' ideological spectrum. Here's Greg Mankiw on Barack Obama's anti-NAFTA stance, including an instructive quote from his colleague Larry Summers on NAFTA's success. Here's Paul Krugman on "Ricardo's Difficult Idea." Finally, here's Brad DeLong explaining why comparative advantage is the most misunderstood concept in economics.

"Trade Promotes Economic Progress" is #4 among the "Ten Key Elements of Economics." Cast of Characters Below the Fold.

Mankiw: economist at Harvard, former chairman of W. Bush's Council of Economic Advisors.

Summers: economist at Harvard, former Secretary of the Treasury under Clinton.

DeLong: economist at Berkeley, former Deputy Assistant Secretary of the Treasury under Clinton.

Krugman: economist at Princeton, staff member of CEA under Reagan, current New York Times columnist and critic of the W. Bush administration, and blogger/author of "The Conscience of a Liberal."