After a second place finish in South Carolina's Republican primary, Marco Rubio laughed off a suggestion by Donald Trump that the Florida senator may not be eligible to run for president. "I'm gonna spend zero time on his interpretation of the Constitution with regards to eligibility and I'm gonna spend all my time talking about what this campaign should be about," Rubio said Sunday on ABC's "This Week." On Saturday Trump retweeted a Twitter user's claim that Rubio is ineligible to be president. When asked about the retweet, Trump said in a separate interview on "This Week" he had never...