When the "Gang of Eight" immigration reform package hits the Senate floor next week, Iowa Sen. Charles Grassley will be running the debate and amendment process for the Republicans.

Senate Majority Leader Harry Reid, D-Nev., has ultimate authority over the floor debate; and as the Democratic "floor manager," Judiciary Committee Chairman Pat Leahy of Vermont carries more muscle to influence the amendment process than Grassley. But the Iowan's role as the GOP floor manager is not insignificant, and could prove consequential, according to Republicans monitoring immigration reform and its prospects for passage.

Grassley, 79, is steeped in the politics and policy of immigration. He has a deep interest in border security policy, and is a farmer who represents a state with an economy fueled by agriculture, an industry typically reliant on cheap immigrant labor. And Grassley, first elected to Congress in 1974, is a veteran of the immigration battles of 1986 (it passed) and 2007 (it failed) and approaches the current debate with that experience in mind.

"Grassley has forgotten more about the politics of immigration than the rest of these newbie senators will ever know," said a Republican operative and longtime Washington hand with relationships in the Senate.

This won't be Grassley's first stint as a floor manager for a politically charged bill; Grassley performed the same role for the Affordable Care Act, a.k.a. Obamacare, a position that fell to him in part because he was at the time the top Republican on the Finance Committee. Now the top Republican on Judiciary, Grassley is once again a central figure in a debate over legislation with broad implications for the economy and electoral politics.

In this role, Grassley could be influential in determining which Republican amendments get a floor vote, and how much debate time proposals receive. More generally, he will be responsible for advocating for the minority party's parliamentary rights, especially if Democrats try to limit Republican amendments in a manner unacceptable to the GOP.

Grassley has been highly critical of the "Gang of Eight" legislation, going so far last week as to sign onto a letter with some of the legislation's most vocal opponents -- Sens. Ted Cruz of Texas, Mike Lee of Utah and Jeff Sessions of Alabama -- who outlined a host of what the authors view as serious flaws. Citizenship for 11 million current illegal immigrants and tougher border security have been the most prominent flashpoints.

But Iowa's senior senator said his skepticism of the bill would not affect his job as floor manager. In fact, Grassley believes the prospects for a civil floor debate and passage are quite positive.

"There won't be a filibuster unless there's an effort on the part of Reid to not have open amendments and open debate -- even if it goes beyond July Fourth," Grassley said. "If Reid has the same patience that Leahy had in committee, then it's going to go pretty smoothly, and I don't know if that's three weeks or four weeks ... As long as you can avoid a Democrat-Republican division on process you'll get a bill through the Senate. Whether I vote for it or not I won't know till we get there."

Grassley said that this latest battle over immigration is different than both the debates over Obamacare and the failed 2007 effort to overhaul U.S. immigration law. The fight over President Obama's health care law split along party lines -- and fiercely. The last attempt to reform immigration regulations went down in part because of strong opposition from the conservative grassroots that Grassley acknowledged has been absent this time around.

Proponents of "Gang of Eight" immigration reform are expecting Grassley to vote "no." And, they believe his opposition to the bill could influence his actions as floor manager.

However, Grassley has a history of bipartisan legislating, so much so that during the health care debate Republicans feared that he would cut a deal with Senate Finance Chairman Max Baucus, D-Mont., and make it harder for the GOP to oppose Obamacare. Grassley spent months as a member of the "Gang of Six" negotiating a health care compromise. However, the senator never casted a vote in favor of the Affordable Care Act, not even in the Finance Committee.

"Grassley will not like amnesty without a secure border and he was fooled once before," the Republican operative said, in regard to the senator's support for the 1986 immigration reform legislation, although he added: "Grassley has the typical farm community view that cheap temporary farm labor is the center of farm economics."