Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: Washington (CNN) Donald Trump on Wednesday likened the presidential race to a boxing match -- saying that victories in next week's Ohio and Florida primaries would give him the knockout blow necessary to capture the GOP nomination. "It's like with the fighters," Trump told CNN's Anderson Cooper. "If you knock 'em out, nothing can happen." Trump said victories in Ohio and Florida would "pretty much" assure exits from Ohio Gov. John Kasich and Florida Sen. Marco Rubio. Recent polls have shown Trump leading in both of those states, which are set to vote Tuesday. "I think if I win those two, I think it's over," Trump said.Donald Trump said victories in Ohio and Florida would "pretty much" assure exits from Ohio Gov. John Kasich and Florida Sen. Marco Rubio"If you knock 'em out, nothing can happen," Trump said 
 Question:In particular, Trump said _, once envisioned as a chief Trump rival who is staking his campaign on a win in Florida next Tuesday, was seriously damaged.

Marco Rubio