Bernie Sanders on Sunday sought to turn fire aimed by Democrats at two of their own, Kyrsten Sinema and Joe Manchin, onto Republican senators he said were “pushing an anti-democratic agenda”.

“Republicans are laughing all the way to election day,” the Vermont senator told CNN’s State of the Union. “They have not had to cast one bloody vote which shows us where they’re at.”

But the Vermont progressive also confirmed that he will campaign against Manchin and Sinema, both Democrats, should they face viable primary challengers.

Manchin, from West Virginia, and Sinema, from Arizona, have blocked Democratic priorities including the Build Back Better spending plan and, this week, voting rights reform.

Their refusal to contemplate reform to the filibuster, the rule which requires 60-vote majorities for most legislation, meant two voting rights bills in answer to Republican attacks on voting in states were always doomed to fail.

On Saturday, Sinema was formally censured by her state party. Sanders said he supported that move. He also confirmed his threat to campaign against Sinema and Manchin in 2024.

“If there was strong candidates prepared to stand up for working families who understand that the Democratic party has got to be the party of working people, taking on big money interests, if both candidates were there in Arizona and West Virginia, yes, I would be happy to support them.”

But, Sanders insisted, “it’s not only those two. It is 50 Republicans who have been adamant about not only pushing an anti-democratic agenda but also opposing our efforts to try to lower the cost of prescription drugs, trying to expand Medicare … to improve the disaster situation in home healthcare, in childcare, to address the existential threat of climate change.

“You’ve got 50 Republicans who don’t want to do anything except criticise the president and then you have, sadly enough, two Democrats who choose to work with Republicans rather than the president, and it will sabotage the president’s effort to address the needs of working families in this country.”

Speaking to NBC’s Meet the Press, Sanders insisted the Biden administration made “a great start”, in part with a Covid relief bill passed with just 50 votes and the casting vote of Vice-President Kamala Harris, but was now bogged down thanks in large part to Manchin and Sinema.

“The president and the Democratic Congress,” Sanders said, “… looked at the economic crisis that was caused by Covid. We passed the American Rescue Plan … and we also passed along the way the strongest infrastructure bill that has been passed since Dwight D Eisenhower … We were off to a great start.

“And then I will tell you exactly what happened. Fifty members of the Republican party decided that they were going to be obstructionist … and then you had two United States senators joining them, Mr Manchin and Senator Sinema.

“For five months now there have been negotiations behind closed doors trying to get these two Democratic senators on board. That strategy, in my view, has failed. It has failed dismally. We saw it last week in terms of the Voting Rights Act. We now need a new direction.”

Asked if he was frustrated, Sanders told CNN he was.

But, he insisted, “we need to start voting. We need to bring important pieces of legislation that impact the lives of working families right onto the floor of the Senate. And Republicans want to vote against lowering the cost of climate change, home healthcare, whatever it may be. And if the Democrats want to join them, let the American people see what’s happening.

“Then we can pick up the pieces and pass legislation.”

Some Democrats advocate splitting Joe Biden’s Build Back Better plan into separate bills, in order to pass what they can.

Sanders conceded that most such legislation will not pass, given Republican obstruction and the machinations of Manchin and Sinema. Bringing bills to the floor, he conceded, would really be about electoral politics ahead of midterms this year in which Republicans expect to take back the House and possibly the Senate, and the presidential contest in two years’ time.

“Once we know where people are at,” he said, “then we can say, ‘All right, look, we have 50 votes here, we have just one vote here, 49 votes here.

“But what has bothered me very much is Republicans are laughing all the way to election day. They have not had to cast one bloody vote, or two, which shows us where they’re at. And we’ve got to change.”