Rubio traveled to Iowa -- which will hold one of the first votes in the 2016 presidential race -- to speak Saturday at a birthday fundraiser for Gov. Terry Branstad. His appearance was one of the first major events for the GOP since Mitt Romney failed to win the presidency this month, Politico said.
Prior to the speech, Rubio told reporters he had circulated a draft immigration bill among his congressional colleagues.
Romney's views on immigration appeared to alienate Hispanics, which some analysts contend cost him the election.
"People understand that we need to do something to address these issues, and we need to do it in a reasonable and responsible way," Rubio said.
In his speech, Rubio spoke of mainstay GOP goals such as lower taxes and fewer business regulations, and rallied the party faithful to continue to work on keeping the United States strong.
"If America declines, there is nothing to take our place," he said. "What country is going to serve as an inspiration?"