Rep. Adam Schiff, D-Calif., on Friday warned of the dangers of Russian meddling in the 2018 congressional midterm elections after special counsel Robert Mueller indicted 12 Russian military officials for federal crimes allegedly committed during the 2016 election cycle.

"Not only was the DNC hacked and Clinton's campaign manager hacked, the DCCC was hacked," said Schiff, the top Democrat on the House Intelligence Committee, during an interview on CNN. "The Russians played in House races, which means that if they follow the playbook from the last cycle, they'll play in the midterms. We obviously need to be doing everything we can to protect against that."

Mueller's indictment, returned Friday in federal court, alleged that 12 Russian officials "engaged in a sustained effort" to break into computers owned by the Democratic Congressional Campaign Committee, the Democratic National Committee, and Hillary Clinton's campaign in the lead-up to the 2016 presidential contest.

The development was announced by Deputy Attorney General Rod Rosenstein just days before Trump is scheduled to meet with Putin in Helsinki, Finland, on Monday. Trump is expected to discuss the topic of Russian interference in the election that catapulted him into the White House.

[White House: New indictments 'consistent' with Trump's message about collusion]

"The president, knowing that there's unequivocal proof that the Russians hacked our institutions, to go into the summit and to continue to make these comments so favorable to Putin and the Russians is utterly inexplicable from the perspective of U.S. national security interests," Schiff continued. "It can only be explained by the fact that Donald Trump has a single ideology that trumps everything else, and that is the ideology of self."

Schiff's prediction was echoed by House Minority Leader Nancy Pelosi, D-Calif., who warned that action needed to be taken before the Nov. 8 elections because "the integrity of our democracy is at stake.”

“The Russians waged a massive, concerted operation to interfere in our elections, and they will do so again in the fall," Pelosi wrote in a statement released Friday. "Strong, immediate action is needed to secure our state election systems, yet Republicans are wasting the country’s time with sham hearings while refusing to provide a single additional penny to protect our elections."

The two Democrats' posturing clashes with testimony offered this week by Christopher Krebs, the Department of Homeland Security's under secretary for national protection and programs directorate. Krebs told the House Homeland Security Committee on Wednesday that U.S. intelligence officers have not found any evidence of a robust effort by foreign agents to tamper with the midterm elections.