Sen. John Cornyn, the second-ranking Republican in the Senate, has just released his much-discussed amendment to the Gang of Eight comprehensive immigration reform bill. The amendment is extensive — 134 pages — and covers a number of areas in measuring and enhancing border security. But perhaps its major feature — certainly the one that Senate Majority Leader Harry Reid has called a “poison pill” — is its insertion of a real border-security trigger into the Gang of Eight bill.

If Cornyn’s amendment were adopted as part of the legislation, the estimated 11 million illegal immigrants who will be made legal shortly after passage of the bill would not be able to apply for green cards a decade later until new border security measures were actually in place. “The Secretary [of Homeland Security] may not adjust the status of aliens who have been granted registered provisional immigrant status,” the amendment says, until:

(A) not earlier than 9 years and 6 months after the date of the enactment of this Act, the Secretary and the Commissioner of United States Customs and Border Protection jointly submit to the President and Congress a written certification, including a comprehensive report detailing the data, methodologies, and reasoning justifying such certification, that certifies, under penalty of perjury, that –

(i) the Secretary has achieved and maintained full situational awareness of the Southern border for the 12-month period immediately preceding such certification;

(ii) the Secretary has achieved and maintained operational control of the Southern border for the 12-month period immediately preceding such certification;

(iii) the Secretary has implemented the mandatory employment verification system required by section 274A of the Immigration and Nationality Act (8 U.S.C. 1324a), as amended by section 3101 of this Act, for use by all employers to prevent unauthorized workers from obtaining employment in the United States; and

(iv) the Secretary has implemented a biometric entry and exit data system at all airports and seaports at which U.S. Customs and Border Protection personnel were deployed on the date of the enactment of this Act, and in accordance with the requirements set forth in section 7208 of the Intelligence Reform and Terrorism Prevention Act of 2004 (8 U.S.C. 1365b)

Cornyn discussed details of the amendment at a Republican senators’ lunch yesterday. The provisions were well received by all the GOP lawmakers, with the exception of Sen. Lindsey Graham, a Republican member of the Gang of Eight who has publicly expressed opposition to adding triggers that would cause Democrats to abandon the immigration deal. The question now is whether Republican senators, with the exception of Graham, will unite behind the bill. Even more crucial is the question of whether Sen. Marco Rubio, the leading Republican on the Gang and the one lawmaker many GOP senators look to for direction on this issue, will support the amendment.