Washington ? On Bob Zoellick’s office wall hangs a portrait of George McClellan, the Union general who was Napoleonic in self-regard but not in martial spirit and who is remembered primarily for his reluctance to fight. “I asked for a good portrait of a Civil War general,” says Zoellick. “I should have asked for a portrait of a good general.”

Zoellick, the most important government official most voters have never heard of, holds a job that is one of the underestimated stakes in this presidential election. John Kerry, who is given to complaining that questions about his policies impugn his patriotism, has said smarmily that as president he will “appoint a U.S. trade representative who is an American patriot.” Zoellick, the man Kerry slandered, is President Bush’s trade representative, and on one day last month in Geneva he did more discernable good for his country than Kerry has done in 20 years in the Senate.

On July 31 the string of setbacks in trade liberalization that began in Seattle in 1999 — five years of growth stolen from the world — ended. The World Trade Organization reached an agreement that the industrialized countries — especially the United States, members of the European Union and Japan — will eliminate their agriculture export subsidies, which inhibit and distort trade, and will make “substantial reductions” in domestic farm supports, starting with a 20 percent cut. Poor countries will make similar cuts. Details, wherein lurks the devil, to follow.

This is not altruism on the part of the developed nations. It is better than that. It is economic rationality.

The publics of those nations will reduce their payments to their own farmers. Those farmers will benefit from an increased velocity of trade in a more open international system. For poorer countries — up to 45 of them are net food importers — the elimination of the rich nation’s export subsidies may mean increased food costs, at least for a while. But increased food prices in the importing countries will be incentives for production by their farmers. And to the extent that those farmers cannot compete with imports, they will be turned toward work in other fields — their countries’ comparative advantages.

America’s agricultural interests are varied and sometimes in conflict. Beef, fruits and vegetables have no subsidies. But Americans pay more than four times the world price of sugar because of a combination of import quotas and tariffs. In general, the farm community — one in three acres is planted for exports, which approach $60 billion annually — supports free trade. Zoellick, who unlike many millions of his obese compatriots is rail-thin, says, “How much can we eat? The markets have got to be abroad.”

Prying open 147 economies at once is a Herculean task. It is axiomatic that as the number of parties to a negotiation increases arithmetically, the difficulty of reaching an agreement increases exponentially. Trade negotiations involving 147 economies are more challenging than a Rubik’s Cube — more like three-dimensional chess.

Zoellick’s aim is to insinuate “some Hamiltonian concepts” into U.S. foreign policy. Remember, he says, that without the sinews of economic strength that Hamilton provided, Jefferson — who despised Hamilton — would not have been able to achieve his greatest triumph, the Louisiana Purchase.

Furthermore, free trade amounts to domestic political reform. This is because tariffs, export subsidies and other forms of protectionism are examples of what economists call rent-seeking — interest groups bending public power for private advantage.

Kerry praises multilateralism in the abstract. However, his trade policy — “fair trade,” which means protectionism with an uneasy conscience — would be much more unilateralist than Bush’s has been.

In the world’s long postwar march, under both parties, toward ever-increasing trade liberalization, the United States has been, in former Secretary of State Madeleine Albright’s phrase, the “indispensable nation.” If it does not push relentlessly, progress stalls. This matters now more than ever. As Zoellick correctly says, his work is one front in the war on terror because liberalizing trade is a means of opening closed Islamic societies and strengthening the modernizers within them.

Kerry may still be, as he was in earlier incarnations, more of a free trader than he now seems while pandering to his party’s base. However, his trade policy would be hostage to Democratic factions — organized labor, especially — whose hostility to free trade will make his trade representative into a McClellan.

Zoellick, who hails from northern Illinois, resembles the pride of Galena, Ill. — U.S. Grant. Lincoln, while enduring McClellan, tersely explained why he liked Grant: “He fights.”

George Will is a columnist for Washington Post Writers Group.