Coming Up on This Week with George Stephanopoulos

— -- In a Sunday exclusive, George is joined by 2004 presidential nominee Sen. John Kerry, D-Mass. Fresh off his endorsement of Sen. Barack Obama, Kerry talks about the 2008 race and why he chose to support Obama over his former running mate John Edwards and Senate colleague Hillary Clinton.

Then, in another exclusive, former Speaker Newt Gingrich, R-Ga., gives his perspective on the coming election. Does either party have a frontrunner? Who will be the strongest nominees?

And on our "Roundtable," EJ Dionne, Claire Shipman, Jay Carney and George Will debate the week's politics.