Joe Lieberman has long gone rogue in his own way. The senator from Connecticut and former Democratic vice-presidential candidate may not be quite out there with that other contender for high office, Sarah Palin.

But Lieberman – a professed liberal who supports access to abortion, gun control and some gay rights – infuriated former allies and Democratic voters in his own state with support for George Bush's war in Iraq, and astonished them by campaigning for John McCain and Palin in last year's presidential election.

Now, in the view of some, he is plumbing new depths of betrayal by using his deciding vote as an independent member of the Senate to hold hostage Barack Obama's reform of America's dysfunctional healthcare system.

Obama, desperate to ensure that the reform bid does not fail, has told congressional leaders to rewrite the legislation to keep Lieberman happy by removing any real competition to private insurance companies in an effort to get it passed by Christmas.

Lieberman's tactics have upset Democratic party members of Congress who are asking why a popular president's agenda is being stalled by a senator who has repeatedly turned his back on his old party. "I have no idea what Senator Lieberman's agenda is," said a Connecticut member of Congress, Chris Murphy. "I have stopped trying to be Sherlock Holmes."

Another member of Congress from Lieberman's home state, Rosa DeLauro, told Politico website: "No individual should hold healthcare hostage, including Joe Lieberman, and I'll say it flat out: I think he ought to be recalled."

Lieberman, 67, used his deciding vote in Congress to help strip out a provision for government-run medical insurance, intended to set up competition to the abuses of private companies, by threatening to filibuster the legislation.

Senate leaders agreed to drop the public option for all in favour of allowing people over 55 to buy into an existing government-run scheme for the elderly. In September, Lieberman supported the measure, as he had when he was Al Gore's running mate. But just as it seemed that a deal was done, Lieberman scuppered it by announcing that he had changed his mind and would block any bill that expanded government insurance coverage. Obama gave way.

Some of Lieberman's critics see his stance on healthcare as shaped by his acceptance of more than $1m in campaign contributions from the medical insurance industry during his 21 years in the Senate. The blocking of public-run competition is a huge relief to an industry that has been increasing premiums far ahead of costs and making huge profits while individuals are bankrupted by chronic illnesses. Many of the medical insurance companies are based in Lieberman's home state.

Lieberman vigorously denies that campaign money influences his votes, and he is far from alone in accepting money from vested interests. But it has raised questions as to why insurance companies donate to Lieberman's campaign if they are not buying influence.

It has also not gone unnoticed that Lieberman's wife, Hadassah, works for a major lobbying firm as its specialist on health and pharmaceuticals. She previously worked at drug companies such as Pfizer and Hoffmann-La Roche.

Others see different forces at work. Lieberman's supporters say he is what a senator should be: a fearless voice prepared to fight for what he believes is right. He says that he is "genuinely an independent", as he demonstrated by allying himself with Bush's neocon agenda in the Middle East while opposing that administration's conservative social agenda. "I agree more often than not with Democrats on domestic policy. I agree more often than not with Republicans on foreign and defence policy," he said on Fox News three years ago.

But detractors paint a picture of a vain, bitter man still stung by his rejection by Democratic voters who came close to scuppering his Senate career three years ago and now revelling in the power he wields to block Obama's first piece on major legislation.

Larry Sabato, a University of Virginia political scientist, says the key to understanding Lieberman is his losing the 2006 Democratic party primary for his own Senate seat. Democratic party voters turned on him because of his support for the Iraq war and torture of detainees in Guantánamo – an issue that divided many Americans.

Lieberman then ran in the main election as an independent with strong Republican backing, and won. But Sabato says he was wounded by losing the primary. "In Lieberman's view the party turned its back on him. From the liberal's point of view he had already turned his back on them. That campaign is the genesis of much of what we see today. Tit-for-tat revenge."

The 2006 campaign threw Lieberman into strange alliances. Rightwing rabble rousers such as the talkshow host Rush Limbaugh and the Fox News presenter Glenn Beck came out vigorously for him despite his liberal social views.

The Republican party pumped hundreds of thousands of dollars into Lieberman's campaign and prominent Republican politicians stumped for him. They were rewarded, either out of principal or bitterness, when Lieberman backed McCain and Palin in the presidential race, ostensibly because he viewed Obama as weak on national security. After that he was forced out of Democratic caucus strategy meetings and policy lunches.

But then came last year's election, which put the Democrats within a whisker of the 60 Senate seats they needed to prevent Republican filibusters. Lieberman held the 60th seat. The party caucus voted to allow Lieberman to remain chairman of the Senate homeland security committee in return for his support. Democrats feel they have been poorly repaid.

Lieberman denies he is acting out of spite. "That's just poppycock," he said. "If I had any sense of vendetta against the Democratic party I wouldn't be in the Democratic caucus today."

He may not be for very much longer. Many in Democratic party, and Connecticut voters who overwhelmingly support public medical insurance, may yet get their revenge on Lieberman.

Sabato says that the senator's extraordinary position, where he retains chairmanship of a prominent committee and his seniority despite breaking with the party, is unlikely to survive next year's midterm elections. "Frankly at that point I expect Democrats to lose two or three seats in the Senate and they will no longer have that super majority of 60 anyway. They will have no incentive to coddle Lieberman. They'll basically say: great knowing you and good luck in 2012 because you're going to need it," he said.

That's when the voters will get a change to turf Lieberman out of the Senate. The Republicans may back him to frustrate the Democratic candidate but the polls suggest that about 30% of those who voted for Lieberman three years ago will not do so again in 2012.

"Obama will be favoured to win a second term despite what you're seeing today," said Sabato. "The economy will have picked up by then and so on. But even if Obama loses nationally he will carry Connecticut handily and that will create coat-tails for any major Democratic nominee. They have to find a strong candidate to run against Lieberman but on the whole I think Lieberman knows he's going to have a very tough race for re-election."

Fight for reform

The healthcare reforms Barack Obama signs into law will be a shadow of the campaign promises of government-run medical insurance that would break the back of exploitative private companies widely viewed as getting rich while millions of Americans lived in fear of illness driving them to bankruptcy.

That vision was battered by scaremongering by the right, including Sarah Palin's notorious allegation that the government would establish "death panels" to kill elderly people who fell ill, and advertising campaigns that misrepresented state-run health services abroad as a socialist nightmare. The insurance firms wielded influence with their campaign contributions to members of Congress.

The bills were also ambushed by religious organisations that managed to get provisions written in to the legislation in effect blocking insurance companies from paying for abortion.

But the greatest attrition came from conservative Democrats hostile to government-run insurance schemes, despite opinion polls showing that a majority of Americans, saddled with expensive but limited insurance, favoured the public option.

The White House continues to insist that what will emerge is real reform that will force the insurance companies to cover the sick, will contain costs and expand access to tens of millions of Americans who are not insured.

But it will be a far cry from the legislation that many Americans had hoped meant that their health would no longer be hostage to profit.