Key Democrats are signaling their rejection of Senate Minority Whip John Cornyn's proposed amendment to the "Gang of Eight" immigration reform bill.

The Texas Republican on Wednesday unveiled a proposal he described as the "antidote" for Republican concerns that the bill is too weak on border security. Cornyn said his amendment would help the legislation garner the GOP support the legislation needs to clear the Senate and gain support in the House. But a Senate aide to a Democratic member of the "Gang of Eight" tells The Washington Examiner that Cornyn's proposal is unacceptable.

"The Cornyn amendment ... would subject immigrants to a "trigger" that is unworkable - period," this aide said. "This effort to make the pathway to citizenship unattainable is a bridge too far and it undermines a key principle of the reform bill. We must have a clear and direct path to citizenship. We want undocumented immigrants to pay their fines, pay their taxes, keep their noses clean and earn the path to citizenship. What we can't do is subject 11 million people to a standard that is not workable and cannot be achieved by their own efforts."

The "Gang of Eight" includes Republican Sens. Jeff Flake and John McCain of Arizona; and Lindsey Graham of South Carolina; as well as Democratic Sens. Bob Bennet of Colorado; Dick Durbin of Illinois; Bob Menendez of New Jersey and Charles Schumer of New York. But politically, the gang is anchored by conservative stalwart, Sen. Marco Rubio, R-Fla.

The Florida Republican has signaled that the border security component of the gang's bill must be strengthened to maintain his support, and the Cornyn amendment is viewed as possible way to ensure he remains supportive of the bill. But if Democrats in the "Gang of Eight" are this quick to oppose it, the amendment's viability as a bipartisan bridge is questionable.

"The Gang of Eight has shown a commitment to do everything possible to strengthen border security," said the aide to the Democratic "Gang of Eight" member. "The bill represents some of the toughest border provisions that we've ever had, building on a decade of massive buildup and hundreds of billions of spending. Our bill adds $6.5 billion in border spending. And we're requiring the completion of a new border security plan before any undocumented immigrant can get a path to citizenship. Further, Senator Cornyn's border security amendment was accepted in the Judiciary Committee markup and it strengthened the bill."