With an immigration package poised to clear the Senate this week, attention is shifting to the House and whether the Gang of Eight legislation's strengthened border security measures might boost the prospects for reform in the Republican-controlled chamber.

The House is considering several of its own immigration proposals and will not use the Senate's comprehensive bill as a basis for debate. But the politics of reform within the Republican Party could be significantly influenced by how the Senate bill is received in conservative circles. And, if the House and Senate end up in negotiations over immigration changes, the Senate bill would obviously figure prominently.

Immediately after reaching agreement on a compromise border security amendment negotiated by Republican Sens. Bob Corker of Tennessee and John Hoeven of North Dakota, the response has been mixed — which at this point is a positive development for the prospects of immigration reform. Among the immediate backers of the Gang of Eight bill as amended by Corker-Hoeven: Fox News Channel's Bill O'Reilly.

However, the legislation's critics are already attempting to discredit Corker-Hoeven by claiming it doesn't actually do what its supporters claim, as my colleague, Byron York, reported Saturday. Accordingly, immigration reform's chances in the House could depend in part on the proponents of the Senate package and their ability to build support for the enhanced border security measures in the final bill.

Even conservatives who might want to support an overhaul of U.S. immigration laws and are willing to offer a pathway to citizenship to millions of illegal immigrants worry that the federal government will never follow through with the Senate bill's mandated border security plan, including completion of 700 miles of fencing, the hiring and deployment of an additional 20,000 border patrol agents and the implementation of a nationwide e-verify system for employers.

That's why some Senate Republicans tried, unsuccessfully, to amend the Gang of Eight package to include a trigger that would demonstrably prove that the border had been secured before a former undocumented immigrant, legalized under the legislation, could move on to citizenship.

With that in mind, I asked Corker and Hoeven on Friday how much confidence Republicans could have that border security enhancements in their amendment could not be discarded by a disinterested president and his or her administration.

Q: On the triggers and border enforcement infrastructure, are you confident that newly legalized immigrants will be prohibited from obtaining permanent residency if the administration ignores the security measures mandated by your amendment?

Corker: The problem with all the triggers that have been laid out before is their subjectivity. ... These triggers are the most tangible triggers that have been discussed. Every American citizen can look and see: Is the fence complete? Are there 20,000 border patrol [agents] on the border or not? Is the technology bought and deployed; is the entry-exit visa system in place? Is e-verify, nationwide, put in place? I don't know how you can have a more tangible trigger, or metric. So, you know, the people who criticize this are just looking, in my opinion, for some way to criticize.

Q: Can you assure fellow Republicans that the bill will prohibit newly legalized immigrants from obtaining federal benefits?

Hoeven: That's exactly one of the things we worked on that took time, is making sure that we covered as many of those bases as we could. ... The No. 1 focus is border security, but we've got a lot of Republicans that had concerns, for example, about the benefits. ... We tried to do as much there as we could.

Q: Will the amendment deliver all that lawmakers were promised it would?

Hoeven: We've done the best we can. And, remember, it still has to go through the House.

david drucker Senior Congressional Correspondent