this was her choice. abc's tahman bradley is joining us now with all of the details. good morning, tahman. >> reporter: good morning, diana. president obama has been quick to defend sebelius, despite all of the problems with healthcare.gov. the former kansas governor has been the public face of the affordable care act. getting grilled at congressional hearings about crashes and other problems. sebelius took heat from republicans about the affordable care act itself. but it appeared she and obamacare had turned the corner last week with a late surge of enrollments for health insurance. just yesterday, she told a senate committee 7.5 million people have signed up. that's likely why sebelius is resigning now. she reportedly told the president she wanted to leave a month ago. president obama will nominate sylvia matthews burwell to replace sebelius. and republicans are looking forward to using her confirmation hearings to get a few more shots at obamacare. diana? >> all right. tahman...