Tonight on Washington Week: February 19, 2016

Few could have predicted that the 2016 presidential election would be unlike any in American history. There are the first-time political candidates, outrageous political sniping and this week Pope Francis was pulled into the political fray. On his return trip from Mexico to the Vatican, the pontiff suggested that Republican frontrunner Donald Trump “is not Christian” because of his harsh campaign promises to deport undocumented immigrants and force Mexico to pay for a border wall.

On the Democratic side, the race between Hillary Clinton and Sen. Bernie Sanders has tightened ahead of the Nevada caucuses and South Carolina primary. While Sanders has been riding a wave of momentum following his decisive win in New Hampshire's primary last week, Clinton has been picking up the endorsements of more than 80 party delegates who will decide the Democratic Party's presidential nominee.

Another political battle is brewing following the sudden death of conservative Supreme Court Justice Antonin Scalia. President Barack Obama has announced that he will select a nominee to fill Scalia's seat. Senate Republicans, who must confirm any appointment, appear committed to blocking any candidate until after the presidential election. GOP presidential candidates are hoping to turn the race for the White House into a referendum on the high court's future.

Joining Gwen Ifill with analysis of the battle between President Obama and Republican lawmakers over a successor to Scalia and how the high court vacancy will play into the 2016 presidential race:

Joan Biskupic, Legal Editor for Reuters and author of “American Original: The Life and Constitution of Supreme Court Justice Antonin Scalia”

John Dickerson, CBS News Political Director and Host, “Face the Nation”

Peter Baker, Chief White House Correspondent, the New York Times

Manu Raju, Congressional Correspondent, CNN