(CNN) - While the future of immigration reform is still in question, Republican Sen. Lindsey Graham of South Carolina, a member of the bipartisan Gang of Eight, predicted the Senate will pass the bill with 70 votes or more.
“I think we're going to have a political breakthrough, that Congress is going to pass immigration reform. I think we're going to get plus 70 votes,” he said Sunday on NBC’s “Meet the Press.” “I've never been more optimistic about it.”
His GOP colleague in the Gang of Eight, Sen. Marco Rubio, doesn't sound quite as confident. The senator from Florida maintains the bill is almost in “perfect shape” but reiterated it needs tweaks to its border security provisions.
Meanwhile, a Democratic member of their bipartisan group, Sen. Bob Menendez, said those changes must not undermine one of the bill’s main provisions, which offers a pathway to citizenship.
The Senate voted last week to begin debate on the bill, and senators have already started filing amendments to the legislation. But the measure’s fate hangs on whether Republicans can find a solution that can win favor among enough representatives in the GOP-controlled House.
Rubio has been aggressive in stating that he may withdraw support from his own bill if the measure does not include language that would further boost border security and enforcement–a requirement for many conservatives.
The Republican senator said “95, 96% of the bill is in perfect shape and ready to go, but there are elements that need to be improved.”
“The vast majority of Americans and conservative Republicans are prepared to support immigration reform, but only if we can ensure we're not going to have another wave of illegal immigration in the future,” he said on ABC’s “This Week.”
Menendez, however, suggested Democrats have already made big compromises, saying the bill adds $6.5 billion in funds for border security and includes senators from border states as authors of the bill. (Republican Sens. Jeff Flake and John McCain of Arizona are part of the Gang of Eight.)
“There are critics of our bill in which - 10 angels could come swearing from above that this is the best legislation for America, and they would say the angels lie. So, those I can never solve or satisfy,” Menendez said on CNN’s “State of the Union.”
The New Jersey Democrat said his party is open to changes in the border plan, but maintained he “cannot support” a requirement that the border be certified secure before undocumented immigrants are allowed to begin their pathway to citizenship.
Senators rejected such a proposal last week by Sen. Charles Grassley, R-Iowa, who wanted to delay the legalization process for millions until the Department of Homeland Security could certify it had effective control over the southern border for six months.
But others in the House still favor a similar effort and may pursue that as an option should the bill pass the Senate.
“We're going to have triggers that can never be achieved in terms of border security as an impediment to the pathway to legalization and citizenship,” Menendez said, fervently disagreeing with the idea.
In the end, he said, he thinks the bill will get enough votes to pass and will win over his colleagues on the other side of Capitol Hill.
“When we hit 60 votes, which we will, I have no doubt that other people will want to be on the right side of history, and that will send a very strong message to the House,” he said.
For his part, Graham cautioned that if Congress doesn't pass reform, Republicans will have little chance of taking back the White House in 2016.
"We're in a demographic death spiral as a party, and the only way we can get back in good graces with the Hispanic community, in my view, is pass comprehensive immigration reform," he said on NBC.
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