Democratic presidential candidates hoping to revive their flagging campaigns have taken aim at billionaire Mike Bloomberg for trying to buy his way into the White House.

Struggling to recover from poor showings in the Iowa caucuses and New Hampshire primary, Elizabeth Warren and Joe Biden took the lead in attacking Mr Bloomberg.

Mr Biden, the former vice president, said on ABC’s The View: “I don’t think you can buy an election,” while Ms Warren took Mr Bloomberg to task for his 2008 comments that ending redlining, a discriminatory housing practice, helped trigger the economic meltdown.

Mr Biden and billionaire Tom Steyer also joined forces in slamming Bernie Sanders after the Vermont senator and self-described democratic socialist won New Hampshire and essentially tied for the lead in Iowa with Pete Buttigieg, the former mayor of South Bend, Indiana.

Mr Biden said Mr Sanders had not done enough to explain how he’d pay for his “Medicare for all” proposal to replace private insurance with a government-run programme.

Mr Steyer said that “refusal to tell us how he will pay for his plan adds unnecessary financial risk to achieving health care as a right for every person”.

Voters, Mr Steyer said, “should have all the facts”.

The sniping reflects the remarkably fluid state of the Democratic race even after two states that typically thin out the field have already voted.

The White House hopefuls are trying to blunt Mr Bloomberg, who gained attention by flooding the national airwaves with hundreds of millions of dollars in advertisements and is on the verge of being admitted into next week’s presidential debate.

The lagging candidates are trying to prove that they still have the mettle to stay in the race, even if their path is becoming increasingly difficult.

Ms Warren told The Associated Press that she has raised six million dollars (£4.6 million) since the February 3 Iowa caucuses, a haul that could silence questions about whether she will soon leave the campaign because of her disappointing showings so far.

She called the race “wide open”.

“There’s a lot of froth,” she said. “It’s going to be a long process.”

Candidates are set to face voters in Nevada, which holds its Democratic caucuses on February 22.

Minnesota senator Amy Klobuchar, whose moderate presidential campaign surpassed expectations in New Hampshire this week, raced to Nevada after a senate vote Thursday to try to keep momentum going.

Ms Klobuchar’s rise is inviting new scrutiny, especially from Pete Buttigieg, who is hoping to keep her from eating into his support among moderate Democrats.

Mr Buttigieg, a target of Ms Klobuchar’s for weeks over what she has characterised as light experience, turned his criticism of Washington politics toward the Minnesota senator.

During the LULAC forum, he took aim at her 2018 vote in the US senate to confirm Customs and Border Protection (CBP) commissioner Kevin McAleenan, who he criticised for “the horrifying conditions that children were kept in”.

Mr Buttigieg said: “I’ve heard some people say that, you know, my experience is not relevant because you have to have Washington experience in order to become a president. But some of those same voices are among those who voted to confirm Kevin McAleenan as the CBP head.”

He is also expected to make a big play for Nevada. But the state could pose a challenge for him as it is the first place he will have to win over voters of colour, something polls have suggested would be difficult.

The result is a muddled middle lane in the primary as Mr Sanders is poised to keep squeaking out victories. On Capitol Hill, Mr Sanders said he thinks “we’re on a path to win the nomination”.

“The key to defeating Trump is to have the largest voter turnout in American history,” he said. “And I think we have the campaign – for a variety of reasons – to do that.”