Rubio on Trump Social Security plan: 'The numbers don't add up'

Thursday night's GOP debate at the University of Miami was noticeably devoid of the sharp personal attacks that have characterized previous gatherings. The first notable exchange centered on a dispute over changes to Social Security.

Front-runner Donald Trump said he would "leave Social Security as is" and would focus on making "our country rich again," while focusing on cutting waste and abuse.

Florida Sen. Marco Rubio countered that "the numbers don't add up."

"Fraud is not enough," Rubio said, adding that trimming foreign aid also wouldn't make up for shortfalls in funding the massive entitlement program (Rubio said he would gradually raise the retirement age).

In case you were wondering, the exchange did not include any references to hand sizes and Trump did not address Rubio as "Little Marco."

Prep for the polls: See who is running for president and compare where they stand on key issues in our Voter Guide

A few moments later, after a slightly more spirited exchange between Trump and Texas Sen. Ted Cruz, Trump remarked that he couldn't "believe how civil it's been up here."