CBS News reports, “Florida Sen. Marco Rubio wasn’t one of the candidates Facebook users spent the most time discussing during the Fox Business Network/Wall Street Journal Republican debate, but his exchange with Kentucky Sen. Rand Paul was the most social moment of the evening.”

“The two senators got in an argument about the wisdom of spending U.S. tax dollars on national defense priorities,” CBS reported.  “Rubio called Paul ‘a committed isolationist’ and argued that the world is a stronger and better place when the U.S. has the strongest military power in the world.”

“Paul challenged his credentials as a conservative,” CBS noted.

“Can you be a conservative and be liberal on military spending?…I want a strong national defense but I don’t want us to be bankrupt,’ Paul replied.”

Politico’s Mike Allen also noted that “Per Facebook Policy Communications: ‘Top social moment of the debate on Facebook: Marco Rubio-Rand Paul exchange on entitlements and defense.”

Sen. Paul was also the overall third most discussed candidate on Facebook after Donald Trump and Ben Carson, and the top discussed candidate among men.

Disclosure: I co-authored Senator Rand Paul’s 2011 book The Tea Party Goes to Washington.