Both McCain and Rubio have offered support for Trump as the Republican's White House nominee, but remain concerned that his provocative comments could alienate moderate and independent voters in their states.
Rubio said he was running in part to keep Trump in check, should he be elected president.
Florida Republican, who announced his retirement from the Senate after ending presidential bid in March, says shooting has 'most certainly has impacted my thinking.'
Delegates earned by Rubio could be handed to Trump or Cruz, but the former candidate is choosing to retain his delegates in an attempt to keep Trump from the nomination and earn support in a contested convention.
Marco Rubio actively fed the frenzy of hate and resentment that ultimately consumed him.
Clinton's victories in Florida, Illinois, Ohio and North Carolina cast doubt on U.S. Sanders' ability to overtake her for the Democratic Party's nomination.
'Israel is a special creation for the Jewish people,' Republican presidential hopeful says ahead of primary contest in his home state of Florida.
Israel was the subject of a heated exchange in last week's GOP debate, with Donald Trump hammered by his opponents for saying he would be a neutral broker of Israeli-Palestinian peace.
A series of Republican favorite-son candidacies may be the only way to stop Trump from picking up the 1,237 delegates he needs to take the nomination.
With a Trump sweep of this week's contests, the frontrunner could begin to secure the nomination, but there are many scenarios to consider.