 -- Republican presidential frontrunner Donald Trump said Supreme Court Chief Justice John Roberts has "turned out to be a nightmare for conservatives," and put some of the blame for Roberts' presence on the Court on 2016 rival Sen. Ted Cruz.

"Cruz fought like hell to get Justice Roberts in there. Justice Roberts turned out to be an absolute disaster, he turned out to be an absolute disaster because he gave us Obamacare." Trump told ABC News chief anchor George Stephanopoulos on “This Week” Sunday.

Trump repeatedly went after Cruz, who served as a law clerk for Supreme Court Chief Justice William H. Rehnquist from 1996 to 1997, saying Cruz supported Roberts when he was nominated to the Court in 2005.

Trump noted that Roberts had two opportunities to overturn the Affordable Care Act, which was most recently upheld by the Supreme Court last summer, adding that Roberts “gave us Obamacare. Almost as much as [President] Obama himself."

"Justice Roberts could've killed Obamacare and should've, based on everything -- should've killed it twice," Trump said. "Ted Cruz is the one that was promoting him."

The 2016 presidential election could be critical for determining the future of the Supreme Court. When the next president takes office, four justices will be over the age of 75: Stephen Breyer, Ruth Bader Ginsburg, Anthony Kennedy and Antonin Scalia.

Trump acknowledged the influence the next president could have on the Supreme Court, and said that is "a very, very important element of what we're doing."

When asked what type of justices he would appoint, Trump said he's going to appoint "conservative judges."

"I'm going to appoint people that have great reputations, that are great with the legal profession," Trump said.