Hillary Clinton, Donald Trump, Gary Johnson, Jill Stein, Ted Cruz, Bernie Sanders, Marco Rubio, Rand Paul, Ben Carson, John Kasich, Mike Huckabee, Carly Fiorina, Chris Christie, Martin O'Malley, Jeb Bush, Rick Santorum, Jim Gilmore, George Pataki, Lindsey Graham, Lincoln Chafee, Bobby Jindal.
Answer:Under the Constitution, the vice president serves as the president of the Senate and presides over the Senate's daily proceedings. In the absence of the vice president, the Senate's president pro tempore (and others designated by him) presides.
