If President Obama turns to his left, the right goes up (literally, sometimes) in arms; if he turns to his right, the left threatens revolt. With leaders of the House’s progressive bloc now saying they won’t support a bill without a public option, is compromise on health care possible? The New York Times investigates one option: a “trigger mechanism” that would activate only if private insurers fail to offer affordable coverage. The idea has emerged in the White House’s negotiations with Senator Olympia Snowe of Maine, the one Republican who is willing to engage over the issue. Under Snowe’s plan, the federal option would be offered in any state where fewer than 95 percent of residents have access to affordable coverage.