WASHINGTON — The bipartisan push to overhaul the nation's immigration laws took a major step forward Monday evening when the Senate endorsed a proposal to substantially bolster security along the nation's southern borders as part of a measure that would provide a path to citizenship for 11 million undocumented immigrants already in the country.
The 67-to-27 vote prevented any filibuster of the plan to devote roughly $40 billion to border enforcement measures, including nearly doubling the Border Patrol force to 40,000 agents from 21,000, and completing 700 miles of fencing.
Opponents of the enhanced security questioned whether the steps would ever be taken and said that the legislation should require that the border be secure before undocumented immigrants could begin to seek legal status.
But the solid bipartisan support for the border security proposal crafted by two Republican senators, Bob Corker of Tennessee and John Hoeven of North Dakota, suggested that advocates of the overhaul had the votes needed to clear remaining procedural hurdles and pass the legislation, perhaps before legislators return home during the July 4 recess.
The Corker-Hoeven plan helped bring on board more than a dozen Republicans who voted Monday to take up the provision, many of whom said they were reluctant to support any immigration overhaul that did not secure the southern border and guard against a future wave of illegal immigrants.
Their amendment will also require a $3.2 billion high-tech border surveillance plan — including drones and long-range thermal imaging cameras — as well as an electronic employment verification system and a visa entry/exit system at all air and sea ports.
All those security measures must be in place before any immigrant can become a legal permanent resident and receive a green card. Corker said the new border security proposal "strengthens this bill, puts it in balance, creates trust with the American people, and creates the kind of pathway that many people are seeking."
Despite a clamoring for stronger border security from many Republicans in the Senate and the House, some leading Republicans dug in against the Corker-Hoeven plan.
John Cornyn of Texas, the number-two Republican in the Senate, said he could not "support an amendment cobbled together at the 11th hour that doubles the Border Patrol without knowing how much it will cost or whether it is even the right strategy."
Other Republicans and advocacy groups opposed to the bill also offered loud complaints.
They said the legislation was drafted behind closed doors by a small group of senators; that the bill was too long and not given ample time for discussion; that the legislation needed to be stronger when it came to border security; and that the Corker-Hoeven amendment was simply a toothless provision intended to give Republicans cover to vote for a bill they still viewed as "amnesty."
On Monday, a group of 14 Republican senators sent a letter to Senator Harry Reid of Nevada, the Democratic leader, calling for a "serious, extensive amendment process."
"This is deeply, deeply disturbing," read the letter, referring to the fact that only a fraction of the amendments filed to the bill had been voted on. "It is effectively shutting down the American people's ability to be heard on this issue through their elected representatives."
A spokesman for Reid, however, pointed out that many of the 14 Republicans were the same senators who had failed to work with Democrats to reach a compromise to bring up more amendments on the Senate floor.
As the procedural vote wound to a close Monday, the two sides were still working on a deal that would allow both Democrats and Republicans to bring up 10 more amendments each to the final bill — an agreement that would probably allow Senator Rob Portman of Ohio to introduce a provision to further strengthen the electronic employment verification system in the bill.
Proponents of the immigration overhaul were also not entirely pleased with the Corker-Hoeven plan. A coalition of groups representing border communities urged senators to reject the amendment, which they called "an example of excessive and wasteful government spending" and a "poorly thought-out policy."
"It is an assault on our system of checks and balances and seriously threatens the quality of life of border residents," wrote the border groups, in a statement.
Other advocates worried that in an effort to garner broad bipartisan support for the bill, Democratic senators were making too many concessions without getting anything in return. The border plan, for instance, also includes a provision by Senator Orrin G. Hatch, Republican of Utah, that would prevent undocumented immigrants from qualifying for Social Security benefits, as well as from receiving federal welfare funds.
"It is a tough pill to swallow, and there is no guarantee it will not get worse later in the process," said Kevin Appleby, the director of migration policy at the United States Conference of Catholic Bishops, referring to the amendment. "If the path to citizenship is further weakened, there could come a tipping point where the bill becomes unsupportable."