— -- In an ABC News exclusive, likely 2016 GOP presidential candidate Wisconsin Gov. Scott Walker comes to "This Week" Sunday.

Plus, retired Gen. Stanley McChrystal, former head of Joint Special Operations Command in Iraq and author of the new book "Team of Teams," discusses the U.S. strategy against ISIS.

And the powerhouse roundtable debates all the week's politics, with Democratic strategist and ABC News contributor Donna Brazile, ABC News political analyst Matthew Dowd, former House Speaker and CNN political commentator Newt Gingrich, and Berkeley professor and former Clinton Labor secretary Robert Reich.

See the whole political picture, Sunday on "This Week."

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