David Jackson

USA TODAY

Donald Trump introduced a new element Sunday into his ongoing battle with Ted Cruz: the Chief Justice of the United States, John Roberts.

Trump is now attacking the Texas senator for endorsing the 2005 confirmation of Roberts. even though Cruz has renounced his support of the chief justice in the wake of two cases upholding President Obama's health care law.

"Cruz fought like hell to get Justice Roberts in there," Trump said on ABC News' This Week. "Justice Roberts turned out to be an absolute disaster, he turned out to be an absolute disaster because he gave us Obamacare."

Cruz, a former colleague of Roberts, said last year he supported President George W. Bush's nomination of the chief justice back in 2005, well before Cruz became a senator.

"That was a mistake and I regret that," Cruz said last year, vowing to nominate totally reliable conservatives to the Supreme Court if he wins the White House. "It wasn't that President Bush wanted to appoint a liberal to the court. It is that it was the easier choice."

Trump, locked in a tight race with Cruz ahead of the Feb. 1 Iowa caucuses, is adding Roberts to a list of criticisms that include Cruz's Canadian birth, his unpopularity with Senate colleagues, and his claim that Trump represents "New York values."

Cruz says Trump is attacking him because he has passed the New York businessman in many Iowa polls.

Given that three of the nine Supreme Court justices will be at least 80 years old when the next president takes office, Cruz and Trump have vowed to make the high court a major election issue. Both have criticized Roberts over the health care rulings.

"Justice Roberts could've killed Obamacare ... should've killed it twice," Trump told ABC. "Ted Cruz is the one that was promoting him."