High-ranking lawmakers from both parties had urged Pierson to resign.
A new lawsuit accuses federal health regulators of violating the Affordable Care Act by keeping proposed 2015 Obamacare rates hidden.
After a disastrous launch, Obamacare has 7.3 million individual plan enrollees. But advocates warn challenges loom.
A private guard who rode an elevator with Obama in violation of Secret Service protocol has convictions for assault and battery, according to reports.
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