U.S. intelligence officials believe Russia is trying to boost Sen. Bernie Sanders (I-Vt.) in the 2020 Democratic primary race as part of its interference in this year’s presidential election, according to Sanders and news reports on Friday.

Sanders moved to quickly and firmly reject Moscow’s involvement. His response was strikingly different from the way President Donald Trump has handled Russia’s meddling since the Republican first received Russian President Vladimir Putin’s support in the 2016 election and then was informed earlier this year that Putin wants to see him reelected.

“Unlike the current president, I stand firmly against their efforts, and any other foreign power that wants to interfere in our election,” Sanders said in a statement he issued after The Washington Post broke the news Friday of the Russian efforts to help him claim the Democratic nomination.

“I don’t care, frankly, who Putin wants to be president,” Sanders said. “My message to Putin is clear: stay out of American elections, and as president I will make sure that you do. In 2016, Russia used internet propaganda to sow division in our country, and my understanding is that they are doing it again in 2020.”

Four years ago, Putin used online support for Sanders to worsen splits within the Democratic Party as he sought to secure Trump’s election. His aim now could be two-fold: exacerbating Democratic divisions again to weaken the anti-Trump coalition while bolstering a Sanders candidacy some political analysts believe Trump would find easy to attack as extreme.

Sanders in his response on Friday focused on the national interest in rebuffing the Russian efforts. Campaigning in California on Friday, he told reporters, “It’s an ugly business, and all of us have got to say, sorry, you’re not going to do this in this election.”

Putin in 2016 could have viewed Sanders’ relative silence on foreign policy beyond criticizing U.S. overreach as a sign he might be sympathetic to Moscow. But the senator has since articulated a vision of foreign policy that’s wary of Putin’s aggressive ultra-nationalism and support for oligarchs. He’s shown that just because he is skeptical of muscular demonstrations of U.S. power like military interventions, he does not endorse forces trying to undermine the U.S. or spread disinformation on Washington’s role in global issues like the Syrian civil war.

In the 2016 campaign cycle, Trump denied receiving Russian support even as he openly invited it. His family and his advisors explored the possibility of such help privately and his aides ensured the GOP’s convention platform adopted a position on Ukraine softer than Republican orthodoxy at the time and in line with Putin’s interests.

Once elected, Trump continued to reject the intelligence community’s conclusion that Russia had interfered in the election and did his best to denigrate and thwart special counsel Robert Mueller’s lengthy probe into the matter. Trump continually has framed the concerns and findings about Russian interference as a personal attack on him by political enemies, and used the power of the U.S. government to push a conspiracy theory that exonerated Moscow.

The New York Times reported last week that Trump became angry with Joseph McGuire, the acting director of national intelligence, for telling House lawmakers ― especially Democrats ― about Putin’s 2020 interference efforts. McGuire was replaced as the acting intelligence chief on Friday by Richard Grenell, a staunch Trump loyalist.

And in the Senate, Republicans are blocking legislation that would require campaigns to be more transparent about offers of foreign assistance.