(CNN) Senate Republicans Monday avoided criticism of President Donald Trump's conduct over the handling of a controversial whistleblower's complaint, with one prominent senator even suggesting the whistleblower is a "leaker" who should be criminally investigated.

It's the latest example of how Republicans are extremely reluctant to criticize the leader of their party even in the face of a growing controversy with many outstanding questions.

The tone was set by Senate Majority Leader Mitch McConnell, a Kentucky Republican, when he opened the chamber floor and blasted Democrats for what he said was a politicization of the issue before the facts were known.

McConnell also refused to tell reporters if he believed the formal whistleblower complaint that's being held back by the administration should be made available to Congress or if Trump was wrong to discuss with the Ukrainian President possible investigations of Joe and Hunter Biden. There is no evidence of wrongdoing by either Joe or Hunter Biden.

"Is it a whistleblower or is it a leaker, I don't know which," said Sen. John Cornyn, a Texas Republican and member of the GOP leadership and Intelligence Committee, who said the matter may fall under the jurisdiction of the Department of Justice for prosecution, not Congress for oversight.

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