By Justin Sink
But a Rasmussen poll released last month showed Rubio's favorability had dropped 15 points among Republicans since February.
A Public Policy Polling survey of Iowa, the first state to vote in the Republican nomination fight, found Rubio earning the support of 10 percent of voters, good for fourth place behind Sen. Rand Paul (R-Ky.), New Jersey Gov. Chris Christie and former Florida Gov. Jeb Bush.