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With President Obama reeling over the disastrous rollout of the Affordable Care Act, "This Week" tackles the big questions facing the Obama presidency in crisis.

Will the White House's proposed fix to Obamacare work? As America's trust in Obama crumbles, can the president recover from the problem-plagued health care launch? And is his second term agenda - and his presidential legacy - at stake?

Sen. Kirsten Gillibrand, D-N.Y., takes on the fight over health care, and the battle to stop sexual assault in the military, Sunday on "This Week."

Plus, Republican Wisconsin Gov. Scott Walker, author of the new book "Unintimidated," discusses the state of the GOP and his own political future following his 2011 battle with unions that made national headlines.

And our powerhouse roundtable debates all the week's politics, with Rep. Adam Kinzinger, R-Ill., PBS "NewsHour" co-host and managing editor Gwen Ifill, former Obama White House senior adviser and ABC News contributor David Plouffe, ABC News political analyst Matthew Dowd, former Vermont Gov. Howard Dean, and Wall Street Journal foreign affairs columnist Bret Stephens.

Plus, fifty years after that fateful day in Dallas, ABC News Chief National Correspondent Byron Pitts looks back on the life and death of President John F. Kennedy, and JFK nephew Patrick Kennedy and documentary filmmaker Ken Burns reflect on JFK's legacy.

And in our "Sunday Spotlight," the founder of security contractor Blackwater USA Erik Prince discusses his new book, "Civilian Warriors: The Inside Story of Blackwater and the Unsung Heroes of the War on Terror."

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