Republican presidential candidates Florida Sen. Marco Rubio and Texas Sen. Ted Cruz once again exchanged blows Saturday night during the Republican debate in South Carolina over their records on immigration reform and whether or not they supported so-called amnesty for people living in the United States without the necessary documentation. Rubio, who once supported a comprehensive immigration reform bill in the Senate that would have granted such amnesty but now says that the American people are not ready for that kind of approach, attacked Cruz for past remarks that seem to indicate Cruz’s support of amnesty.

A 2013 video shows Cruz advocating for an amendment to Rubio’s immigration reform bill that would take away a pathway to citizenship from the bill but would still make it possible for undocumented immigrants to apply for and get legal status to “take them out of the shadows.” He proceeds to say that he does not want immigration reform to fail.

The Republican candidates are locked in a contentious nominating contest as the next primary, in South Carolina, approaches Feb. 20. Cruz and businessman Donald Trump were the victors in the first two states to vote, Iowa and New Hampshire, beating out the candidates favored by the establishment Republican Party. Rubio and Ohio Gov. John Kasich made strong showings in those states, however it is not clear that Republicans will rally around any single establishment candidate in the near future.

Trump leads in South Carolina, 17 points ahead of second place Cruz with 35.7 percent of the vote, according to an average of polls from Real Clear Politics . In national polls, Trump also leads, just as he has for the majority of the past six months. That lead could be in jeopardy, however, as Trump has taken a steep dive since the beginning of the month. At the same time, Rubio has enjoyed a steep increase and is coming close to tying second-place Cruz, according to RCP .

Following the voting in South Carolina, the candidates will compete in the Nevada caucuses on Feb. 27. While Trump leads there, polls in the state are notoriously unreliable and are conducted infrequently. The last time that the state was surveyed was in late December and at that time Trump led with 33 percent of the vote over Cruz, with 20 percent and then Rubio, who had 11 percent.