A billboard taking aim at U.S. Sen. Marco Rubio is expected to be installed next week in Georgia, said the head of a conservative group that is behind the effort.

The group is unhappy with the Florida lawmaker because of his central role in a bipartisan Senate bill that seeks to reform U.S. immigration laws by, among other things, tightening enforcement, expanding the guest worker program and providing undocumented immigrants a path to legal status.

It is his support for giving undocumented immigrants an opportunity to legalize – while continuing to live and work in the United States – that most upsets them.

“There’s the betrayal factor,” said D.A. King, who helped draft several of Georgia’s anti-illegal immigration laws. “It’s a mystery to us why he’s still considered a conservative.”

“In his race for the Senate, Rubio said that he would never support any amnesty,” said King, head of the The Dustin Inman Society, described as a non-partisan coalition of citizens against illegal immigration. “If there was any real intention to secure the borders it would have been done after 1986, or after 2007 in preparation for what is happening now.”

Rubio has come under attack from several fellow conservatives since he became part of the so-called “Gang of Eight,” made up of four Republicans and four Democrats in the Senate who worked on a comprehensive immigration bill. 

Last month, for example, a Tea Party group in Rubio’s Florida district held a protest against him, and several of his Republican colleagues in Congress singled him out when criticizing the Senate measure.

Rubio has hit back, sending emails nearly every day shooting down what he says are myths and distortions about the immigration bill. In particular, he has taken apart the whole contention that a path to legal status is tantamount to amnesty.

Rubio has argued that amnesty would be to pardon the undocumented immigrants, but that the Senate bill requires those who seek legal status to pay fines, show that they’ve paid taxes, and wait more than 10 years before acquiring permanent legal status, commonly called “a green card.”

Rubio has said that those who oppose providing a path to legal status are, in fact, supporting an “amnesty” by allowing the estimated 11 million undocumented immigrants to continue living in the United States, under the radar.

On Wednesday, a conservative group called the American Action Network (AAN) announced the launch of a $300,000 television advertising campaign on Fox News Channel, featuring Rubio, to build support for the Senate bill and “calling on Congress to end ‘de facto amnesty.’”

“Our broken immigration system is hurting our country and our economy,” said American Action Network President Brian O. Walsh. “While it isn’t perfect, this reform legislation is tough and fair, and a lot conservatives will embrace it when they hear the facts.”

King, who erected a billboard recently taking aim at U.S. Lindsey Graham, a South Carolina Republican that also is one of the "Gang of Eight," insists that it would be another amnesty.

"Most people aren't going to play the silly game of defining a word," he said. "It's a legalization program. Maybe we need a redefinition of the word conservative, it's more than just not being a Democrat."

Last week, a bipartisan House group introduced bills on agricultural reform and E-Verify, a system for employers to check the eligibility of prospective workers. Proponents of the House's approach to immigration have said separate bills addressing various aspects of immigration stand a better chance of approval than a single, massive bill.

Elizabeth Llorente can be reached at elizabeth.llorente@foxnewslatino.com

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