As the Senate debate over the Gang of Eight comprehensive immigration reform bill reaches full speed this week, leading Democrats have pronounced the border security amendment proposed by Republican Sen. John Cornyn a “non-starter.” To break through what could become a deadlock, other GOP senators have been working on an alternative border security proposal to strengthen the bill in a way that could win support from both Republicans and Democrats. It’s not at all clear that is even possible; the answer to that question could decide whether the Gang of Eight bill succeeds or fails.

The not-yet-released amendment is the work of Sens. John Hoeven of North Dakota and Bob Corker of Tennessee. It is similar to the Cornyn amendment in that it would require that enhanced border security measure be finished and in place before legalized immigrants in what is known as Registered Provisional Immigrant, or RPI status, are allowed to move on to permanent legal, or green card, status. But the amendment would differ from Cornyn by actually outlining, in significant detail, the program of new security measures that would have to be finished before immigrants could move forward.

“What we do is we put the border security plan right in the bill and say, this is the minimum of what you have to do,” Hoeven told me Monday night. “You can’t have people going to green card status until that is in place and you have a way to measure it.”

“It’s different [from Cornyn] in that we actually put the plan right in the legislation,” Hoeven continued. “We’re spelling out all the technologies — drones, Vader, sensors, towers, helicopters…It’s sector-by-sector, the things that the Border Patrol wants.”

The plan would require that the Department of Homeland Security reach a level of apprehending or turning back 90 percent of the people who try to cross the border illegally. “You have to have not only the plan in place but the metric has to be met, prior to going to green card status,” said Hoeven. The requirement would not apply to so-called Dreamers and agricultural workers who are given a special status in the Gang of Eight bill. But for all the others among the estimated 11 million currently-illegal immigrants, the bill would specify that green card status is conditional on enhanced security measures actually being in place.

The question is whether Democrats would accept an actual condition which would have to be met before immigrants can move on to green card status and, later, to citizenship. “We’ll see,” said Hoeven. “It’s under discussion.”

So far, Democrats have opposed any triggers that would impose conditions before immigrants move toward a path to citizenship. Democrats pronounced those conditions a deal-killer with the Cornyn amendment, and it is difficult to see why they would be any more acceptable in the Hoeven-Corker amendment. It is possible that the new amendment’s standard of measuring border security — 90 percent apprehension plus turnbacks — might be more acceptable to Democrats. But if Sen. Charles Schumer and his fellow Democrats felt that any feature of the amendment might in any way slow or impede the march to citizenship, it seems likely they would oppose the amendment.

If Democrats do in fact reject the amendment, then the key question will be how strongly Republicans will support it. Most Senate Republicans probably approve of the Cornyn amendment and will likely be fine with the Hoeven-Corker amendment, too. The issue is whether Republicans will vote against the Gang of Eight bill if it doesn’t have something like those amendments. As Hoeven said, we’ll see.