President Barack Obama celebrated when sign-ups for his health care law topped 8 million, far exceeding expectations after a slipshod launch. Most Americans, however, remain unimpressed. A new Associated Press-GfK poll finds that public opinion continues to run deeply negative on the Affordable Care Act, Obama's signature effort to cover the uninsured. Forty-three percent oppose the law, compared with just 28 percent in support. The pattern illustrates why the health care law remains a favored target for Republicans seeking a Senate majority in the midterm elections.