Sen. Harry Reid, then Democratic majority leader, left, speaks with GOP leader Mitch McConnell in 2014. They sparred in the Senate, and many point to their leadership for an increase in partisanship.

Sen. Harry Reid, then Democratic majority leader, left, speaks with GOP leader Mitch McConnell in 2014. They sparred in the Senate, and many point to their leadership for an increase in partisanship.