Republican presidential rivals Marco Rubio and Ted Cruz have been in a fight over immigration recently. At the center of that conflict is the Gang of Eight comprehensive immigration reform bill, which divided the Senate -- and the Republican party -- over one of the current campaign's most contentious issues. Here is a look at who did what, and when.
The bill passed the Senate after a series of votes in June, 2013. Democrats, who controlled the Senate at the time, unanimously supported the bill, while most Republicans opposed it. The four Republicans on the Gang -- Rubio, John McCain, Lindsey Graham, and Jeff Flake -- of course voted for it, and also agreed with Democrats on a plan to kill almost all GOP amendments.
Then-Majority Leader Harry Reid allowed just a handful of amendments to reach the Senate floor. One, from Republican Sen. Charles Grassley, would have prohibited the legalization of illegal immigrants in the United States until after the administration could prove it had maintained "effective control" of the borders for six months.
Rubio voted against the Grassley amendment. Cruz voted for it.
Another Republican amendment, from Sen. John Thune, would have required the completion of 350 miles of fencing along the U.S. border that Congress had ordered in 1996 but had never been completed. Thune specified that the fencing had to be in place before legalization could commence. Thune also would have required the completion of 700 miles of such fencing before illegal immigrants' legal status could be made permanent.
Rubio voted against the Thune amendment. Cruz voted for it.
The other substantive GOP amendment allowed by Reid was from Sen. David Vitter. It would have delayed the granting of legal status until a biometric visa identity system first ordered by Congress in 1996 had been "fully implemented at every land, sea, and airport of entry" into the United States.
Rubio voted against the Vitter amendment. Cruz voted for it.
Earlier, Republicans offered dozens of amendments to the Gang of Eight bill when it was making its way through the Senate Judiciary Committee. Under a pre-arranged plan, the Gang, including Rubio, agreed to kill any amendments they felt would threaten their legislation.
"The eight met in private before each committee hearing, hashing out which amendments they would support and which oppose as a united coalition," the Washington Post reported in May, 2013. "Senate aides said amendments were rejected if either side felt they would shatter the deal."
For example, the Post reported, "GOP members of the group opposed several tough border-control amendments from Sen. Ted Cruz."
The public discovered the secret Rubio-Democratic agreement when the Judiciary Committee was considering an amendment which involved giving government payments to former illegal immigrants through the Earned Income Tax Credit program. Sen. Charles Schumer, the leading Democrat on the Gang of Eight, was caught on an open microphone turning to an aide and saying, "Do our Republicans have a pass on this one, if they want?" It turned out they did, meaning Schumer would allow Gang Republicans to vote against the measure.
Rubio was not on the Judiciary Committee, so he did not vote on the committee amendments. But he was part of the Gang agreement to kill GOP amendments, several of which were from Cruz, who was on the committee.
The Gang of Eight bill came up for a final Senate vote on June 27, 2013. Rubio, as a key author of the legislation, voted for its passage. Cruz voted against it.
It's worth going through history because Rubio, now locked in a tough presidential primary race, has argued that his position on immigration is similar to Cruz's.
"The bottom line is there isn't that big a difference between (Cruz) and I on how to approach immigration," Rubio told CBS News recently.
Certainly in 2013, Rubio and Cruz could hardly have been more different in how they approached immigration. Rubio has since distanced himself from the Gang bill -- his signature achievement in his nearly five years in the Senate -- saying that immigration reform cannot be accomplished by one giant bill and instead should be enacted piecemeal. Rubio also says -- reminiscent of the Grassley amendment he helped kill -- that security and enforcement must be in place before illegal immigrants can be legalized and placed on a path to citizenship.
It remains unclear where Rubio stands on the thousands of other provisions in his 1,197-page Gang of Eight bill. In five Republican presidential debates, he has been asked exactly one question about the substance of the bill. (The question was whether Rubio still supports a path to citizenship; he does, while Cruz doesn't.)
There's a chance Rubio will be asked more questions about the specifics of the Gang bill in the weeks before Republicans begin voting in primaries and caucuses. It's not clear what he will say, although after the recent Las Vegas debate, a spokesman offered a preview of Rubio's answer.
"The provisions in the 2013 bill were the product of compromise and not what we would have done if we'd written the bill on our own," Rubio aide Alex Conant said. If a President Rubio undertook immigration reform, Conant added, the results "would not be the same as what the Senate passed in 2013."
That reasoning gives Rubio a rationale to abandon any part of the Gang of Eight that he chooses. But what happened in 2013 still matters. For one thing, it's not that long ago. And for another, Rubio himself believes the past is important. "If you're going to attack someone on a policy issue," Rubio said on CBS Sunday, "you need to be clear about where you stand on the issue and where you've stood in the past.