Bernie Sanders smeared as communist sympathizer as Hillary Clinton's allies sling mud
Senator Bernie Sanders (Brookings Institution/Flickr)

Attacks on Bernie Sanders by rival Democrats are likely to turn increasingly to his record on the economy and foreign affairs, according to a new dossier seen by the Guardian that accuses him of sympathising with communists and “not believing in capitalism”.

A ferocious war of words between Hillary Clinton and Sanders has erupted in recent days as polls showing the Vermont senator taking the lead among Democratic voters in both New Hampshire and Iowa have sent shockwaves through the party establishment and prompted growing personal attacks.

On Thursday, Sanders aides accused David Brock, a political operative who runs a Super Pac set up to defend Clinton , of “mudslinging” after he claimed Sanders was acting as if “black lives don’t matter” in a new campaign ad.

This follows a week of steadily mounting criticism from other campaign surrogates such as Chelsea Clinton, who accused the senator of wanting to “dismantle Obamacare” , and foreign policy adviser Jake Sullivan who warned that Sanders’s proposals for tackling Isis would put Israel at risk .

Such characterisations are vigorously rejected by Sanders who argues his healthcare plans build on Obama’s reforms and that a regional coalition is necessary to defeat Isis in Syria.

But the attacks are likely to intensify nonetheless in the days leading up to the Iowa caucus according to a new document that delves into affiliations and statements made by the senator dating back decades.

Related: How the Iowa caucuses work: a confusing election process explained

The dossier, prepared by opponents of Sanders and passed on to The Guardian by a source who would only agree to be identified as “a Democrat”, alleges that Sanders “sympathized with the USSR during the Cold War” because he went on a trip there to visit a twinned city while he was mayor of Burlington.

Similar “associations with communism” in Cuba are catalogued alongside a list of quotes about countries ranging from China to Nicaragua in a way that supporters regard as bordering on the McCarthyite rather than fairly reflecting his views.

Sanders has insisted on many occasions this year that his own philosophy of democratic socialism is very different to that of authoritarian regimes, and much more in keeping with the tradition of American reformers such as Franklin D Roosevelt.

The Vermont senator has also ridiculed suggestions – repeated by the attack dossier – that his policies would see nationalisation of US industries.

“I don’t believe government should take over the grocery store down the street or own the means of production,” he said during a speech at Georgetown University. “But I do believe that the middle class and the working families who produce the wealth of America deserve a decent standard of living and that their incomes should go up, not down. I do believe in private companies that thrive and invest and grow in America, companies that create jobs here, rather than companies that are shutting down in America and increasing their profits by exploiting low-wage labor abroad.”

In his current stump speech, repeated on Thursday night in New Hampshire, Sanders acknowledges “we live in a highly competitive global marketplace” but calls for better education as a response.

“One of the reasons our campaign is doing well is because we are treating the American people as if they are intelligent human beings,” added the senator in the lake resort town of Wolfeboro.

Asked about the rise of the personal attacks during an earlier stop in Hooksett, Sanders spokesman Michael Briggs said they were “nonsense” and only prove how rattled Clinton supporters have become by signs of waning popularity among voters

Briggs later issued a statement condemning the latest public attack on the campaign for airing an advert expand=1] only containing a handful of non-white faces. “From this ad, it seems black lives don’t matter much to Bernie Sanders,” Brock said in an interview with the Associated Press.

“Bernie Sanders, as everyone knows, has one of the strongest civil rights records in Congress. He doesn’t need lectures on civil rights and racial issues from David Brock, the head of a Hillary Clinton Super Pac,” responded Briggs in his statement.

“25 years ago it was Brock – a mud-slinging, right-wing extremist – who tried to destroy Anita Hill, a distinguished African American law professor. He later was forced to apologize for his lies about her. Today, he is lying about Sen Sanders. It’s bad enough that Hillary Clinton is raising millions in special-interest money in her Super Pacs. It is worse that she would hire a mudslinger like David Brock. She should be ashamed of her association with Brock.”

Brock recently denied reports that he was questioning Sanders’ health, but admitted he was preparing to raise the issue and was chastised for it by Clinton campaign chairman John Podesta . © Guardian News and Media 2016