Sen. Rand Paul (R-Ky.) said on NBC's "Meet the Press" Sunday that he thinks it's a mistake for the White House to argue there was no quid pro quo with Ukraine to investigate President Trump's political rivals, and that Trump has "every right" to condition military aid on fighting corruption.

"I think we've gotten lost in this whole idea of quid pro quo. ... If you're not allowed to give aid to people who are corrupt — there's always contingencies on aid. ... Presidents since the beginning of time have resisted Congress, and there's been this sort of back and forth jockeying over what is sent. But also presidents have withheld aid before for corruption. I think it's a mistake to say, 'Oh, he withheld aid until he got what he wanted.' Well, if it's corruption and he believes there to be corruption, he has every right to withhold aid."

— Rand Paul

Why it matters: Paul will act as a juror in the Senate trial in the likely event that Trump is impeached by the House. His argument that there's nothing wrong with using military aid as leverage to push Ukraine to carry out investigations is one of several shifting strategies that defenders of the president have deployed.

Democrats counter that Trump has displayed no interest in fighting "corruption," as Paul argues, and that the investigations he wanted Ukraine to pursue specifically concerned the president's domestic political rivals — Joe Biden and the Democratic National Committee.

Bloomberg also reported on Saturday that the State Department "quietly authorized" the release of $141 million of the aid to Ukraine after lawyers found that the White House had no legal standing to block the funds, which had been appropriated by Congress.

Worth noting: Paul told NBC's Chuck Todd that he opposes aid to Ukraine altogether. "I wouldn't give them the aid because we don't have the money," the senator said. "We have to actually borrow the money from China to send it to Ukraine, so I'm against the aid and I think it's a mistake to do the aid so I wouldn't have played any of these games."

Go deeper: The GOP's war over naming the Ukraine whistleblower