Marco Rubio Sen. Marco Rubio (R-Fla.) (Haraz N. Ghanbari/Associated Press)

Florida Sen. Marco Rubio (R) took his sales pitch on a new bipartisan immigration plan to perhaps his most hostile audience yet Tuesday, calling in to conservative talk show host Rush Limbaugh's daily radio program.

In return, Rubio got some coveted praise from the influential host, who declined to label him a RINO squish for negotiating with Democrats over a new blueprint for a sweeping overhaul of immigration laws that would provide a new path to citizenship for illegal immigrants.

During the nearly-15-minute interview, Limbaugh expressed deep skepticism about efforts to change immigration laws, insisting that President Obama has no interest in fixing the immigration system but instead wants to use the issue to bludgeon the GOP with Latino voters.

Still, he said, Rubio's own efforts were "admirable and noteworthy."

"You're meeting everybody honestly, forthrightly. You’re meeting everyone halfway," Limbaugh said. But he quickly added his concern: "Obama is seeking political victory. Obama doesn’t care about enforcing existing law, so people say, why would he enforce anything new?"

Obama will unveil his own immigration proposal in a Las Vegas speech Tuesday. Rubio said Tuesday's speech will serve as a key test for the president.

"The president has an important decision to make here," Rubio said. "He can either decide he wants to be part of a solution, or he can decide that he wants to be part of a political issue and try to trigger a bidding war. I’m not going to be part of a bidding war, to see who can come up with the most lenient path forward."

Rubio, who has been making the rounds with conservative pundits, has received a surprisingly warm reception for his efforts to craft a comprehensive immigration overhaul with Democrats. On Tuesday, he practically pleaded with Limbaugh and his vast audience to keep an open mind about the project. Rubio said Republicans must engage Democrats on the issue or risk letting Democrats forever label the party as racist and anti-immigrant.

"In the absence of moving forward with our own principles, the left and the president will tell people what we stand for. And it’s not necessarily going to be true," Rubio said.

He also insisted that he will not sign on to final legislation that does not make a path to citizenship for the nation's estimated 11 million illegal immigrants, contingent on improving border security and other enforcement measures.

The broad blueprint unveiled by four Democrats and four Republicans on Monday would allow illegal immigrants to quickly obtain probationary legal residency. But they could not pursue a green card until the border is secure. How exactly that would work must be negotiated before the group introduces a bill.

"If there’s not language in this bill that guarantees that nothing else will happen unless these enforcement mechanisms are in place, I will not support it. But the principles clearly call for that," Rubio said.

Obama is unlikely to insist that citizenship be tied to improving border security, which Limbaugh predicted would scuttle the effort.

"The fear that many people have is that the Democrats don’t want border security. They want this influx. If 70 percent of the Hispanic vote went Republican, do you think the Democrats would be for any part of this legislation?" Limbaugh said.