Sen. Rubio’s point of no return

Legislating in the Senate usually goes like this: A senator introduces a bill, touts it and puts pressure on the House to take it up.

But Sen. Marco RubioMarco RubioFlorida: 'High likelihood' of first Zika transmission in the US Overnight Healthcare: Rubio presses Obama to spend Zika money | FDA moves ahead with trans fat ban The Trail 2016: Her big night MORE has taken a very different approach. The Florida Republican, who helped craft the Gang of Eight immigration reform bill, has recently said the legislation should be altered and can’t pass the GOP-led House unless it is.

Those comments sparked speculation that Rubio was getting cold feet. After all, the reform bill has been taking hits from both the left and the right.

But the senator on Tuesday dismissed any notion that he is distancing himself from the bipartisan plan. The possible 2016 White House candidate believes the immigration bill should be improved through amendments. As far as his comment about the House is concerned, Rubio says he was just making a realistic observation.

Sen. John McCainJohn McCainMcCain granddaughter comes out in support of Clinton With reservations, moving toward Hillary Clinton FULL SPEECH: Hillary Clinton closes out Democratic convention MORE (R-Ariz.), also a member of the gang, maintains that there is backing from right-leaning House members, including Budget Committee Chairman Paul RyanPaul RyanKoch officials skeptical of Trump's alleged meeting invite Trump draws backlash for comments on slain soldier's father Muslim DNC speaker challenges GOP leaders to call Trump out MORE (R-Wis.).

Over the last several weeks, The Hill has talked to some House conservatives about the proposal. It is true that they are not fond of the Gang of Eight’s bill, most notably its provision of a path to citizenship.

But the gang is a tight group, and all its members are in a boat together. Rubio is tasked with steering that boat through rough waters on the right.

On Monday, Heritage Foundation President Jim DeMint went on the attack, releasing an analysis that says the bill’s price tag would be $6.3 trillion.

Rubio has been respectful of DeMint, but on Tuesday he called Heritage’s findings “flawed.”

He faulted the “single premise” that “these people are disproportionately poor because they have no education, and they will be poor for the rest of their lives in the U.S. Quite frankly that’s not the immigration experience in the U.S.”

In many ways, Rubio has little choice but to stick with the legislation. In 2012, he said he was going to unveil the GOP version of the Development, Relief and Education for Alien Minors (DREAM) Act, but he backed away from that plan after accusing President Obama of playing election-year politics.

There is no doubt that he must stay with the Gang of Eight if the bill, or some version of it, is going to become law. Without his imprimatur, conservative members will vote “no” and the legislation will die.

If that happens, Obama would suffer a stinging setback. But so would Rubio.

The freshman senator is working on a range of issues in this Congress, including a bipartisan education bill with Sen. Chris CoonsChris CoonsTop Dem: ‘I don't believe for a minute’ Trump was joking about Russia The Hill's 12:30 Report Senators ask IRS to issue guidance to help startups MORE (D-Del.). Last year, he delivered speeches on foreign policy and visited the military prison at Guantánamo Bay.

Still, Rubio’s 2016 presidential run — if he launches a bid — will be shaped around the success or failure of immigration reform.