The Republican presidential candidates engaged in a lengthy exchange midway through Thursday night's Republican debate in Houston with pointed attacks on each other’s records. While under fire for his past support of Democrats and liberal policies, businessman Donald Trump took a shot at Texas Sen. Ted Cruz and accused him of being partly responsible for the Affordable Care Act, aka Obamacare.

Trump said Cruz supported the nomination of Chief Justice John Roberts in 2005 and made a point of mentioning that Roberts’ votes were integral to upholding the Affordable Care Act, in what was otherwise considered a conservative court.

“This is a rough thing and I know Ted feels badly about it,” Trump said of Cruz’s support of Roberts just over a decade ago. “I think he probably still respects this judge.”

Cruz quickly countered, saying he did support the nomination once it was made. He then said that he would’ve nominated his former boss, Mike Luttig, if he had the choice.

What Cruz thought about Roberts before he was nominated is hard to say, but he does have a history with the chief justice. In 2000, when tasked with putting together the legal team to support President George W. Bush in front of the U.S. Supreme Court against Vice President Al Gore — a case that decided the presidential election in Bush’s favor — Cruz chose to reach out to Roberts for the gig.

“John had been a friend and [former Chief Justice William] Rehnquist clerk — I’ve known John a long time,” Cruz told the New Yorker magazine in a 2014 profile.

Heading into Super Tuesday — where a big portion of the nomination's delegates will be decided — the outlook to beat Trump does not look good for either Cruz or fellow Sen. Marco Rubio, who is from Florida. Trump leads the two senators in all but three of the 12 mostly Southern states lined up to vote.  But even in two of the states where Trump is trailing, his delinquency is decidedly modest. Cruz is in first place in polling in both Arkansas and his home state of Texas, but is ahead of Trump by an average of only 4 percent and 4.7 percent, respectively. Retired neurosurgeon Ben Carson, who once seemed to be running an ascendant and promising campaign but has since dropped in a big way according to polls, leads the pack only in Colorado, where he is followed by Rubio 6 percent behind him and then Trump 2 percent further.

That Cruz is trailing in so many states in the South is significant. His campaign has been geared toward exciting Christian conservatives, and the Bible belt certainly has plenty of those sorts of voters. Further evidence of Cruz’s general vulnerability in the 2016 GOP race can be seen in that 4.7 percent lead in Texas. While some polls show the Texan leading Trump by better figures than that average, others show the two in virtual ties, according to Real Clear Politics.