Calling it a mission behind enemy lines might be an overstatement. White House Chief of Staff Rahm Emanuel didn't actually crawl beneath barbed wire or observe radio silence as he made his way from his office to the imposing limestone structure directly across Lafayette Square.

But when the president's top aide sat down last week with the U.S. Chamber of Commerce board of directors, it marked a meeting of political combatants in a relationship that in recent weeks had grown increasingly adversarial.

Emanuel's appearance came after several rocky weeks for the chamber. The business lobby endured the defection of high-profile members such as Apple over its opposition to proposed climate-change legislation, was punked by a left-wing group that staged a phony press conference in its name and even saw the president publicly brand one of its ads "completely false."

Suddenly, the nation's largest business group found itself in the political cross hairs as it has on few occasions in its 97-year history. And the stakes could scarcely be higher. As the economy leaves behind its once-in-a-century emergency and grinds into recovery, the federal government is more deeply engaged in the market than at any other time since World War II.

"My job is to represent the broad-based business community. ... We know who we are, and we know what we're doing," says Tom Donohue, the chamber's pugnacious president.

Neither side is seeking a scorched-earth battle. The chamber wants its voice heard on scores of issues, many of which never rise to public attention. And President Obama needs business to create jobs to support his No. 1 priority: shrinking the economically draining and politically threatening jobless rate.