The Senate immigration bill got a boost Thursday, when a bipartisan group of lawmakers agreed to a “border surge” amendment that would double the number of border agents and spend $3.2 billion on equipment to seal off the southern border.

Republican Sens. John Hoeven of North Dakota and Bob Corker of Tennessee unveiled the amendment Thursday afternoon and it quickly attracted more Republican votes to the bill (S 744). All four Republicans in the “gang of eight” who drafted the legislation are co-sponsors of the amendment.

Corker said he thought the amendment, if adopted, could give the bill the support of up to 15 GOP senators, including the four Republicans in the gang of eight. That would provide momentum as the bill heads to the House, where passage of an immigration overhaul is expected to be much more difficult.

Two GOP senators, Mark S. Kirk of Illinois and Dean Heller of Nevada, announced their support Thursday for the Hoeven-Corker amendment.

Kirk had previously contended the bill did not go far enough to enhance border security, but on Thursday he said another 20,000 border agents, “one every 1,000 feet,” would seal the border to his satisfaction and allow him to vote for the bill.

Heller said he could back the bill provided that the amendment is adopted and that no adverse changes are agreed to before final passage.

“A lot of us wouldn’t have come along if [Corker and Hoeven] didn’t work as hard as they did to put this package together,” he said. “This border-first amendment that strengthens the language in this particular piece of legislation is something I can support.”

The long-awaited amendment, expected to be formally introduced Thursday evening, came together over the past few days in a marathon series of meetings between Hoeven, Corker and Democratic negotiators.

Many Republicans have complained that the bill’s border security provisions are too vague and give too much discretion to the Homeland Security Department.

Democrats, meanwhile, have rejected proposals — such as one from Sen. John Cornyn, R-Texas — that would impose hard “triggers” on border security that could delay or complicate the path to citizenship for people living in the country illegally.

On Thursday, senators from both sides said the Hoeven-Corker amendment had found middle ground.

“It solves the riddle of how we deal with border security, without allowing somebody in future years who is against citizenship to impede that path,” said Sen. Charles E. Schumer, D-N.Y., a member of the gang of eight. “I think it’s a real breakthrough.”

Sen. Marco Rubio, R-Fla., a fellow author, called the Hoeven-Corker amendment “our chance to fix” the bill.

Senate Majority Whip Richard J. Durbin, D-Ill., another member of the group, said the amendment could bring on board “a substantial number of Republicans.”

“I knew at the beginning, when the negotiations started, that Republicans were going to insist on a dramatic show of force on the border,” Durbin said. “I think it goes beyond what is necessary, but this is a compromise.”

Likewise, Sen. Robert Menendez, D-N.J., said he believes the bill as currently drafted has enough votes to pass, but the amendment will “significantly increase the vote in the Senate.”

$3.2 Billion Investment

Corker said the amendment should put his fellow GOP colleagues’ minds at ease.

“If this amendment passes, which I hope it will, I don’t know how anybody could argue that the reason they’re not supporting this legislation is because we haven’t addressed securing the border,” Corker said. “We have addressed that in spades in this legislation.”

Unlike the original bill, which left the southern border strategy up to the of Homeland Security Department, the Hoeven-Corker amendment would write details of that plan broken down by border sector directly into the law.

The amendment would require a $3.2 billion investment in technology such as cameras, helicopters or drones to help border agents. The number of armed officers patrolling the border would also double to roughly 40,000.

The amendment also mandates that the administration complete 700 miles of fencing along the border. It demands that the E-Verify employment verification system be put in place and that better entry and exit systems are installed at all airports to better track those who overstay their visas.

Once those conditions are met — and senators expect them to be met relatively easily — the roughly 11 million undocumented immigrants currently in the country would be allowed to move toward legal permanent residence.

Earlier versions of the amendment included a requirement that border officials apprehend or turn back 90 percent of those spotted trying to cross illegally. Democrats rejected that requirement, saying it could delay or prevent undocumented immigrants from becoming citizens.

Boost From the CBO

The Congressional Budget Office analysis released Tuesday gave the amendment talks new momentum by predicting the immigration bill would increase tax revenues and reduce the federal budget deficit by $197 billion over 10 years. Those savings made it a lot easier for senators to propose spending more money on the border.

“The breakthrough was when I sat down with Chuck [Schumer] and Corker and we said, ‘Let’s go big.’ Once we got the CBO score back, we said, ‘Go big on the border,’” said Sen. Lindsey Graham, R-S.C., a gang of eight member.

Schumer called the CBO report “a game changer.”

Not everybody is happy with the amendment, however.

Sen. Jeff Sessions, R-Ala., said the amendment would not do enough to secure the border.

“The bill would remain, it appears to me, weaker than what [was defeated] in 2007,” Sessions said, referring to the last comprehensive immigration overhaul attempt in Congress.

Sen. David Vitter, R-La., said the amendment does not address the fact that the legislation would allow legalization before securing the border.

“It is an immediate amnesty … and then this attempt at enforcement after that,” Vitter said. “We need to fundamentally reverse that order.”