A border security amendment overcame a key procedural hurdle in the Senate Monday, paving the way for the most sweeping legislative changes to immigration reform in decades.
The Senate voted 67 to 27 to move forward with the immigration bill.
The bill, which would double the number of border security agents to 41,000 and spend an additional $3.2 billion on drone technology and additional fencing, was a key step to win over Republicans who expressed concern that the underlying legislation left the border too porous.
The amendment will require border security to be bolstered before immigrants who entered the country illegally are eligible for green cards.
"We have satisfied those who want border security and those who want a path to citizenship," Sen. Chuck Schumer, D-N.Y., said on the Senate floor. "No one can dispute that the border becomes virtually air tight."
Some Democrats made it clear they were not satisfied with the additions, but voted to advance the amendment because it ushered in an opportunity to a path to citizenship for the 11 million immigrants who had entered the country illegally.
"This is not the amendment I would have drafted," Sen. Patrick Leahy, D-Vt., said, but "because their amendment will increase Republican support for this historic, comprehensive legislation, I will support it."
The bill won the support of key Republicans who had been on the fence, including Sen. Orrin Hatch, R-Utah, Sen. Dean Heller, R-Nev., and Sen. Mark Kirk, R-Ill.
But the legislation failed to win over everyone. Some argued the amendment, while it attempted seal up the border, came at too high a price and recklessly prescribed a one-size-fits-all solution to the border.
"This bill puts the resources in the wrong place," says Sen. Tom Coburn, R-Okla. "This bill has no teeth. This bill has $48 billion thrown up against a wall to buy the votes to say 'We are going to have a secure border,' when in fact we will not."
The disagreements over the legislation also underscored the divided Republican caucus and vast divide between potential Republicans who may throw their hat into the 2016 presidential ring.
Sens. Ted Cruz, R-Texas and Sen. Rand Paul, R-Ky., for example, strongly opposed the legislation and called it a "fig leaf." While Sen. Marco Rubio, R-Fla., an original architect of comprehensive immigration reform who has wobbled in his support for the legislation since it has been introduced, welcomed the bolstered border security with open arms.
Some GOP hardliners outside of the Senate applauded the border provision.
Arizona Gov. Jan Brewer, who has enacted some of the toughest immigration laws in the country, said Sunday on Fox News that the Senate's border plan "is a great step forward."
"I am glad that they finally decided to talk about the border surge, that we have called out for since 2010, asking them to take control of our border," Brewer said.
The legislation will likely get a final vote before the July 4 recess.
But the future of the bill is uncertain in the House, where a divided GOP caucus struggles to support a path to citizenship and the House Judiciary Committee has been working to pass piecemeal enforcement bills, instead of the sweeping Senate bill.
House Speaker John Boehner has said he will not bring any bill to the floor that cannot attract a majority of his caucus.