Liberal HBO comedian John Oliver attacked moderate Democrats in the Senate on Sunday for not wanting to end the filibuster.

In a segment of his show "Last Week Tonight" that was posted by NewsBusters, Oliver argued ending the filibuster, which is used to prevent bringing a measure to a vote, is the best chance of passing bills to "help curb state-level attempts at voter suppression."

"The best shot those bills have at getting enacted is if Democrats end the filibuster," Oliver said. "And to do that, every Senate Democrat would need to be on board. The problem there is, one of those Democrats is [Sen.] Joe Manchin."

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Oliver said Manchin, D-W. Va., is among several Senate Democrats, including Kyrsten Sinema, D-Ariz., and Dianne Feinstein, D-Calif., who have expressed support for the rule.

"It’s not just Manchin," Oliver said. "Democrats like Kyrsten Sinema and Dianne Feinstein have also defended the filibuster. And both Biden and Harris have been lukewarm on the issue in the past, which is very frustrating."

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Oliver argued Democrats should take stronger stances to meet the "drastic levels" of their Republican counterparts.

"Democrats simply cannot afford to rest on their laurels right now," Oliver said. "Republicans definitely aren’t! They’ve made it abundantly clear they’re willing to take things to drastic levels. And Democrats just don’t seem remotely prepared to meet that threat right now."

"But you know what? You know what? Don’t worry," Oliver added. "I’m sure the GOP will simply put the past behind them, recognize what they’ve done wrong, and shepherd all of us into a bipartisan era of mutual cooperation for the common good. That was sarcasm."

NewsBusters, a conservative site and media watchdog, blasted Oliver's call for Democrats to attain more power.

"If comedy is making fun of the powerful, Oliver truly has given up. He’s now an operative for the state," Scott Whitlock wrote.

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Oliver is an alumnus of Comedy Central's "The Daily Show" and, like most late-night hosts, overwhelmingly favors Democrats and lampoons Republicans in his routines.