Pool/Getty Images

Russian interference in the 2016 election "is really the political equivalent of 9/11 — it is deadly, deadly serious," said former Undersecretary of Defense Michael Vickers, who served in the Obama administration, in an NBC News interview Saturday. "The Russians will definitely be back, given the success they had," he added. "I don't see much evidence of a response."

Vickers' comments come one day after The Washington Post's comprehensive report detailing former President Obama's inaction in response to Russian election interference in 2016. President Trump and congressional Democrats have also criticized the Obama administration's "inadequate" response.

Read The Week's analysis of how Russia weaponized the internet here.