Florida Republican Sen. Marco Rubio has embarked on a high-risk, high-reward mission. His goal? Convince conservatives to support the bipartisan immigration reform measure he and his "Gang of Eight" colleagues have drafted. The success or failure of his effort will go a long way toward determining both whether reform passes, and where Rubio fits into the conservative movement going forward.

As last week showed, Rubio has his work cut out for him.

Sen. Marco Rubio (R-Fla.). (Jewel SamadAP)

Since signing off two weeks ago on the bill that offers a path to citizenship to illegal immigrants, bolsters border security and creates a new guest-worker program, Rubio has been taking to the airwaves to defend the measure against detractors on the political right, who have complained the bill offers "amnesty" and is being jammed through by liberal Democrats.

On Thursday, Rubio launched a Web site designed to dispel myths about the bill and took his case to a crucial medium in the conservative sphere, talk radio.

"I don't understand why we're doing something that the Democrats are salivating over," declared conservative commentator Rush Limbaugh on his Thursday show, adding: "I'm having trouble seeing how this benefits Republicans."

Rubio responded that the imperative for action is twofold. The current immigration system is broken, he contended, and the nation's laws are not enforced. "So, for those two reasons alone, we have to do something," said the senator.

Limbaugh, who in a January interview with Rubio seemed warmer to reform, pressed him about securing the border and questioned whether it was politically wise to clear a path for new Hispanic voters, whom data show tend to align more closely with the Democratic Party. And in interviews with four other conservative talkers, Rubio failed to win over the hosts.

He's also had to push back against claims in the conservative blogosphere that the bill would give immigrants with work visas free cell phones, and deal with protests from tea party activists.

Rubio's most crucial task, Republican strategists say, is to win the arguments on border security and the path to citizenship.

"I think the biggest challenge, and what will ultimately decide this issue, is convincing conservatives that real border security is going to be a part of any package and that there are strong accountability measures and enforcement mechanisms," said Florida Republican strategist Tim Baker.

Added Rick Wilson, another Florida-based GOP strategist: "If he successfully explains border security -- the provisions of which are really quite remarkable -- and the steepness of the path to citizenship, I think he can sway conservative audiences."

Rubio appeared well aware of his biggest challenges, addressing conservatives directly during a "Gang of Eight" press conference last week.

"Let me close with one final point to my fellow Americans who share my commitment to limited government and free enterprise, who helped elect me in 2010," Rubio said. "I would just remind them, America is a nation of immigrants." To those worried about "amnesty," Rubio offered a counterargument: "Leaving things the way they are, that’s the real amnesty."

As conservatives have urged caution in the immigration debate following the Boston Marathon bombings (the two bombing suspects were members of an ethnic Chechen family that received asylum in the U.S. in 2002), Rubio said Monday that he disagrees with those who say the attack has no bearing on the debate.

"If there are flaws in our immigration system that were exposed by the attack in Boston, any immigration reform passed by Congress this year should address those flaws," he said in a statement.

If Rubio fails to win sufficient GOP support and the bill dies, it will be a blow to the political standing of the politician viewed widely as one of the GOP's best options for the 2016 presidential race. On the other hand, if he succeeds, then his stock in the party is likely to soar to even greater heights.

Politically, having Rubio on the "Gang of Eight" helps both Democrats and Republicans. For Democrats who have long clamored for reform, having a stamp of approval from one of the country's most prominent conservatives -- who is Hispanic, no less -- is a huge plus. And for Rubio, taking part in the effort is an opportunity to be the most prominent Republican to tackle an issue many see as fundamental to repairing the GOP's relations with the Hispanic community.

"Marco is uniquely situated to do this and he and his team have obviously prepared," said Florida Republican strategist Ana Navarro, an early supporter of Rubio in his 2010 Senate campaign. "They understand that if misperceptions about this bill are created early and stick, the bill dies and he is whacking at every attempt to mislead."

After all, if Rubio can't sell the conservative base on immigration reform, it would be hard to argue that any Republican can.

The 20,000 foot political question as this debate unfolds is whether having the ideal Republican on board as a chief advocate is enough to help the pro-reform crowd break through to skeptical conservatives, who hold sway in the Senate, and wield even more clout in the GOP-controlled House. So far, it isn't clear that it will be.

Updated at 1:22 p.m.