President Donald Trump fired off on a diverse range of topics this weekend, from the Obama administration's dealings with Iran to Oprah Winfrey.

His latest salvo on Twitter began Friday and rolled out in a series of 16 posts, peaking early Sunday with a tweet about Russia.

"I never said Russia did not meddle in the election, I said 'it may be Russia, or China or another country or group, or it may be a 400 pound genius sitting in bed and playing with his computer,'" Trump posted early Sunday. "The Russian 'hoax' was that the Trump campaign colluded with Russia — it never did!"

On Friday, Deputy Attorney General Rod Rosenstein announced that a federal grand jury had indicted 13 Russian nationals as part of special counsel Robert Mueller's probe and had charged them with fraud, conspiracy, identity theft and other crimes. According to the indictment, some of the methods the Russians used included supporting Trump's campaign and "disparaging" then-Democratic presidential candidate Hillary Clinton.

While Trump has emphasized that his campaign didn't collude with Russia, the president has never condemned Russia since his inauguration more than a year ago, and lawmakers say it's more than concerning.

"That we don't have a president speaking out on this issue is a horror show," Sen. Bernie Sanders, I-Vt., told Chuck Todd on NBC's "Meet the Press" on Sunday. "We got to bring Democrats and Republicans together — despite the president — to go forward and protect the integrity of American democracy."

Sanders called Trump's continued opposition to the Russia investigation "one of the weirdest things in modern American history," and he said, "People are asking what is going with this president?"

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"The main point to be understood is that what everybody understands except Donald Trump is that this was not just the 2016 campaign," Sanders said, adding that the Russians "intend to do this in 2018."

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Sen. James Lankford, R-Okla., also said the president's current position was problematic, but he later added that the Department of Homeland Security was working to secure state election systems.

Nevertheless, he said, Russia had clearly made a push to undermine U.S. democracy with a pattern of attempted influence that stretched back to 2014.

"Russia has clearly tried to advance their agenda into the United States," the senator said. "The president has been very adamant to say that he didn't collude. He's very frustrated that people seem to accuse the fact that the only reason he's president is because of some sort of Russian collusion. But I would say the clear message here is Russia did mean to interfere in our election."

Others in Congress also were scratching their heads Sunday as the president continued to press against the Russia investigation.

Adam Schiff, D-Calif., the ranking member on the House Intelligence Committee, said Sunday on CNN's "State of the Union" that Russian interference "is now overwhelming and unequivocal." He also said Trump had dropped the ball in his role as president.

"It is inexplicable that the president of the United States continues to sit on sanctions that Congress passed — that Congress wants enforced against Russia over this interference," Schiff said, referring to the Trump administration announcement released late last month.

The Mueller indictments should be enough proof for the Trump administration, Schiff said.

"It ought to put to rest, for anyone, including the president, who continues to call this a witch hunt, that the evidence is now overwhelming and unequivocal," Schiff said.

Schiff also made an appearance in Trump's Sunday morning tweets, as he said, following the release of Friday's indictment, that the Obama administration may not have been tough enough on the Russia's interference during the 2016 election.

Finally, Liddle’ Adam Schiff, the leakin’ monster of no control, is now blaming the Obama Administration for Russian meddling in the 2016 Election. He is finally right about something. Obama was President, knew of the threat, and did nothing. Thank you Adam! — Donald J. Trump (@realDonaldTrump) February 18, 2018

Sanders touched on Obama's response, as well, on "Meet the Press" on Sunday.

"Look, Obama was in a very difficult position," Sanders said. "He did not want to make it appear that he was favoring Hillary Clinton. Maybe he should have done more."

Related: The charges Mueller could have brought against the Russians but didn't

Sanders' 2016 campaign — along with Trump's — was named in Friday's indictment as one that the Russian nationals used to sow discord in the election system and to buoy criticism of Clinton.

Sanders said, to the best of his knowledge, no one in his campaign has been interviewed in the Mueller probe, although he said the campaign tried to warn the Clinton campaign that something fishy was going on.

"One of our social media guys in San Diego actually went to the Clinton campaign in September and said: 'Something weird is going on. Bernie's not in the campaign. Hundreds of these people are now coming onto his Facebook site,'" Sanders told Todd. "So I think we already knew that it was an effort to undermine American democracy and to really say horrible things about Secretary Clinton."

Finally, in a late Sunday post, Trump took aim at Oprah Winfrey’s 60 Minutes show on CBS, claiming she posed "biased and slanted" questions to a panel.

He called the host “insecure,” adding that he hoped she would run for office so "she can be exposed and defeated just like all the others."