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The most ambitious and potentially historic bill that Congress may see this term is now being debated in the full Senate. It's the bill to revamp immigration laws and it's a high priority of President Obama's. He's repeatedly pushed back at Republicans who insist on more border security. And today, the president took the time to speak about it again, in advance of the Senate debate.
PRESIDENT BARACK OBAMA: Today, illegal crossings are near their lowest level in decades. And if passed, the Senate bill - as currently written and as hitting the floor - would put in place the toughest border enforcement plan that America has ever seen. So nobody is taking border enforcement lightly.
CORNISH: After President Obama's statement, the Senate took their first floor vote on immigration bill. By a vote of 82 to 15, they agreed to move forward.
But as NPR's David Welna reports, partisan division still make the bill's prospects uncertain.
DAVID WELNA, BYLINE: Before joining all but 15 of his GOP colleagues in voting to bring up immigration bill, Minority Leader Mitch McConnell made clear he has problems with this legislation, which many Republicans think might help stanch eroding support among Latino and Asian voters.
SENATOR MITCH MCCONNELL: The bill has serious flaws. I'll vote to debate it and for the opportunity to amend it. But in the days ahead, there will need to be major changes to this bill if it's going to become law.
WELNA: And the most important change, McConnell said, is making the bill tougher on border security. Key to that, he said, is an amendment being offered by Texas Republican John Cornyn. It would not let the 11 million unlawful immigrants obtain green cards until there is 100 percent surveillance of the U.S.-Mexico border, and at least 90 percent of those sneaking across it are apprehended. Cornyn rejected Democratic charges that his measure is a poison pill, aimed at killing the bill rather than improving it.
SENATOR JOHN CORNYN: If we don't guarantee to the American people that we actually are going to get serious about stopping the flow of people illegally crossing our southwestern border - or the northern border, for that matter - I think we guarantee the failure of bipartisan immigration reform. That is the real poison pill.
WELNA: Cornyn's proposal is playing well on the GOP side of the aisle. Arizona Republican Jeff Flake belongs to the bipartisan gang of eight which drafted the bill.
SENATOR JEFF FLAKE: There's been some talk about some kind of poison pill. That's not the case. Cornyn is trying to get language that he can support, so we're working with him.
WELNA: Even Democratic leader Harry Reid hinted today he may bend on the issue. He noted the bill already beefs up security along the Mexican border.
SENATOR HARRY REID: But if there ways that people feel that we can do better to make the security important and that isn't some just reason to try kind of kill this, let's take a look at it.
WELNA: But New York Democrat and gang of eight leader Charles Schumer is not budging.
SENATOR CHARLES SCHUMER: There are certain principles which we will not cross, such as a path to citizenship.
WELNA: But the voice that may prove most influential in this debate is coming down on the side of making green cards depend on tighter security. Florida Senator Marco Rubio is a member of the gang of eight, who insist the bill has to get tougher if it's going to become law.
SENATOR MARCO RUBIO: What many in the advocate community and many of my Democratic colleagues are asking for is certainty on the green card process. Which is fine, but what about certainty on the border? I think they both require certainty. And I don't think asking for certainty that the border is going to be secured is an unrealistic request.
WELNA: It's a debate that could split the unity of the gang of eight and with it, the bill's bipartisan backing.
David Welna, NPR news, the Capitol. Transcript provided by NPR, Copyright NPR.