“Over the last three months, Marco Rubio’s name and face and voice have been so attached to the comprehensive immigration bill that it has virtually killed any enthusiasm among Republicans in Iowa for a Rubio presidential candidacy,” said GOP State Central Committee member Jamie Johnson. “Most Republicans here now see Rubio as the amnesty candidate.”

“Rubio seems to be so damaged it will be very difficult for him to recover here in Iowa,” said Rep. Steve King. “My perspective is that the immigration issue will sort Republican candidates.”

“Rubio has hurt himself immeasurably with his support of the current immigration bill,” said Sioux City conservative radio host Sam Clovis. “The rule of law still trumps all the feel-good aspects of the bill.”

“Immigration will be a separator issue, for sure,” said Chuck Laudner, a longtime GOP activist allied with King and an influential supporter of Santorum in 2012.