Donald Trump takes part in a CNN town hall event in Milwaukee on Tuesday. Darren Hauck/Getty Images hide caption
John Kasich
Wednesday
Thursday
Clockwise from top left: Hillary Clinton, Donald Trump, John Kasich, Ted Cruz and Bernie Sander Justin Sullivan; Andrew Harrer; Ralph Freso; Bob Levey; Brendan Smialowski/Getty Images hide caption
Listen: Hillary Responds To Critics Allegations
A polling station in Oakmont, Pa., on Nov. 6, 2012. Winning a presidential nomination includes mastering complex rules about delegates, and Pennsylvania's rules are among the most complicated. Jeff Swensen/Getty Images hide caption
In This GOP Primary, You Can Win The State But Get Only A Few Delegates
Tuesday
Republican presidential candidate Ted Cruz addressed the Brussels attacks on Tuesday morning in Washington, D.C. Win McNamee/Getty Images hide caption
Tuesday
Bernie Sanders and Hillary Clinton stand together Wednesday before the start of the Democratic presidential debate at Miami Dade College in Miami. Wilfredo Lee/AP hide caption
Friday
Donald Trump reacts during a campaign rally in Fayetteville, N.C., Wednesday. Gerry Broome/AP hide caption
Tuesday
Bernie Sanders addresses a rally at Macomb Community College in Warren, Mich. Sanders needs a good showing in Michigan on Tuesday to start to turn his campaign around. Scott Olson/Getty Images hide caption
Friday
Marco Rubio and Donald Trump participate in the Republican presidential debate in Detroit. Geoff Robins/AFP/Getty Images hide caption
Thursday
Donald Trump gestures Thursday as Sen. Marco Rubio, R-Fla., listens to Trump's response during a Republican presidential primary debate in Detroit. Paul Sancya/AP hide caption
Donald Trump addresses a crowd in South Carolina. Trump has the clearest path to the GOP nomination, but Republicans opposed to him aren't giving up the fight. Spencer Platt/Getty Images hide caption
Donald Trump addresses Marco Rubio in one of their many heated exchanges during a debate last week in Houston. Gary Coronado/AP hide caption
Sunday
Donald Trump greets supporters after speaking at a caucus night watch party at the Treasure Island Hotel & Casino in Las Vegas. Trump is favored to do well Super Tuesday. Ethan Miller/Getty Images hide caption
Tuesday
Bernie Sanders and Donald Trump deliver victory speeches at their respective watch parties in New Hampshire. Jewel Samad/AFP; Joe Raedle/Getty Images hide caption
Republican Chris Christie of New Jersey has invested nearly his entire campaign on New Hampshire. A poor result will almost certainly effectively end his candidacy. Robert F. Bukaty/AP hide caption
Monday
Donald Trump flashes a thumbs up after finishing second in the Iowa caucuses last week. Jim Watson/AFP/Getty Images hide caption