WASHINGTON — In August 2011, as President Obama prepared to unveil a major new environmental regulation on smog, his political advisers issued a warning: The rule would affect power plants and factories throughout the Midwest, slowing the economy in states like Ohio that would be crucial to the president’s re-election.

In a move that enraged environmentalists, Mr. Obama ordered the Environmental Protection Agency to delay what industry groups were calling the most expensive regulation in history.

Four years later, Mr. Obama has no more re-election worries, and environmentalists have won a court-ordered deadline of Thursday for the E.P.A. to release the smog rule. But the regulation remains as divisive as ever. Over the past month, as the agency and White House senior officials have worked to complete it, the nation’s most powerful business groups — including the Chamber of Commerce, National Association of Manufacturers, Business Roundtable and American Petroleum Institute — have united on an all-fronts lobbying and advertising campaign to ensure that the rule, when it comes this week, is as weak as possible.

“The costs of doing this are not going to be absorbed by a magic sponge,” said Jay Timmons, the chief executive of the manufacturers group, which has been joined by dozens of mayors and governors, including many Democrats. “The impact is going to be largest on manufacturing. The tighter the standard, the more localities are impacted.”