The ozone almost did her in.

Lisa Jackson, the Environmental Protection Agency administrator, was on the verge of quitting two weeks ago after President Obama rejected her centerpiece proposal for strict new air-pollution regulations, The Post has learned.

Jackson told intimates she had been convinced Obama would back her up despite aggressive lobbying from Capitol Hill Republicans and business interests.

But on Sept. 1, she learned her support in the West Wing had crumbled during two meetings — one with Chief of Staff Bill Daley and another with the president.

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