In the midst of these bitterly contested, hyper-partisan midterm elections, one of the most interesting subplots is how the left-leaning, Bernie Sanders-inspired Democrats will fare – and what that could mean for the future of US politics.

Alexandria Ocasio-Cortez’s congressional victory in New York in June was a high-water mark for the left. Backed by Sanders and the Democratic Socialists of America, Ocasio-Cortez crushed the Democratic insider Joe Crowley in what some heralded as a socialist dawn.

But since then some of the other Democratic candidates running on progressive platforms have faltered, falling to more traditional centrists. Which raises the question: is the US ready for a wave of democratic socialism?

The GOP is betting that it isn’t. Republicans are attempting to tie the Democratic party as a whole to progressives like Sanders and Ocasio-Cortez. They believe swing voters can be intimidated by talk of socialism – a move most recently demonstrated on Tuesday when the White House published a 72-page dossier warning of “the opportunity costs of socialism”.

Scaremongering and misrepresentation aside – the document links Sanders and the Massachusetts senator Elizabeth Warren to Karl Marx, Lenin and Mao Zedong – the publication at the very least shows the level that leftwing ideas have permeated American discourse since the 2016 election.

And despite Sanders’ ultimate failure to win the nomination, and the mixed fortunes of democratic socialists since, organizers on the left insist they are at the start of something big – even if that something takes time to materialize.

“One parallel could be when Barry Goldwater lost in 1964,” said Waleed Shahid, a director at Justice Democrats, a progressive organization that works to elect candidates like Ocasio-Cortez. Goldwater, a Republican, won just six states in the 1964 presidential election but his opposition to government intervention – including opposing the 1964 Civil Rights Act – arguably laid groundwork for the future of the GOP.

Shahid said: “There was a whole generation of conservative activists, organizers, intellectuals who felt emboldened to kind of plant the seeds of a movement, and that movement ultimately 16 years later led to Ronald Reagan.

“And I feel like when Bernie Sanders loss in 2016 is similar to that where I think that just ushered in a whole new generation of candidates, organizers, intellectuals who feel emboldened now.”

Shahid said Ocasio-Cortez plus candidates like Andrew Gillum, running for governor of Florida, and Ben Jealous, running for governor of Maryland, have been able to run for national office because of Sanders’ presidential campaign.

Organizers are hopeful of successes in the short term but they are also looking beyond. Activists are confident they can achieve that Goldwateresque long-term impact.

Maria Svart, the national director of the Democratic Socialists of America, said: “We’re building the socialist wing of a broader movement that is really pushing this country and will definitely be pushing Congress, but at the same time we are an organization that wants to build at the grassroots for the long term.

The Democratic party used to think that the way to win elections was through appealing to moderate white suburbanites Waleed Shahid

“So we’re building the pipeline of people that will run for office. On November 7 we’re already going to be thinking about who’s going to be running in 2019 and 2020 for local office.”

Like Shahid, Svart sees hope in what conservatives have been able to achieve with a similar approach.

She said: “I grew up in the 80s when the evangelical wing of the state built the grassroots army – and they now control the supreme court.”

The DSA saw a membership spike in the year following Sanders’ run for president and Trump’s election. By the end of 2017 it had more than 32,000 dues-paying supporters nationwide. Shahid believes many people had “given up on electoral politics” until Sanders came along – which he says explains why movements like Occupy Wall Street sprang up outside traditional political avenues.

Sanders showed people that a democratic socialist can break through at a national level, Shahid said. “And now you need a new generation of leaders who want to actively engage in politics.”

Progressive candidates had mixed success in this summer’s Democratic primaries. In June NPR reported that only two of the six candidates backed by Sanders for the US House won their primaries – and one was an incumbent. But there are signs their policies are having an impact.

Since Sanders’ run for president, his ideas have entered the mainstream, most visibly in the increased support in the Democratic party for single-payer healthcare. The “Medicare for All” plan Sanders released in 2017 now has the support of a third of Senate Democrats, including 2020 frontrunners like Kamala Harris, Elizabeth Warren and Cory Booker.

In July this year at least 70 Democratic members of Congress formed the Medicare for All caucus in the House, while National Nurses United, a trade union that represents more than 180,000 nurses, surveyed all Democratic candidates running for the House in 2018 and found that 52% of those running support a Sanders-style plan.

Bernie Sanders’ ‘Medicare for All’ plan has found favor among many Democrats. Photograph: Meg Kinnard/AP

A number of polls have found that a majority of voters – including Republicans – support some form of universal healthcare. On Tuesday a survey by Hill.TV and HarrisX found 70% of Americans support “providing Medicare to every American”, with 52% of Republicans in favor, numbers which were almost identical to a Reuters/Ipsos poll from August.

Shahid said: “Most of the candidates who are thought to be running [for president] in 2020 are tacking very closely to Sanders’ platform.

“[Sanders’ success] has had an enormous effect on the Democratic party. The Democratic party used to think up until basically 2016 that the way to win elections was through appealing to moderate white suburbanites, usually upper middle class. The whole political calculation for many Democrats has changed to: ‘How do we activate young people? How do we activate people of color how do we activate people of all backgrounds?’”

But for all the excitement among those on the left, some believe it is too soon for a full-scale embrace of progressive ideas. Republicans have already adjusted their message during this midterm elections season to seize on some of the more left-leaning messaging from candidates – that White House dossier being just the latest example.

Bill Galston, a senior fellow at the Brookings Institution, a political thinktank, said: “If Democrats become the party of ‘Abolish Ice’, ‘Medicare for All’, and ‘Impeach Kavanaugh and Trump’, they would expose themselves to attack when the focus otherwise would be on the errors and excesses of the president and congressional Republicans.”

Booker and the like would be unlikely to consider themselves socialists, but if they do cling to at least some elements that marked Sanders’ presidential run, then their actions speak louder than their stated political positions.

In any case for Shahid, the White House is not the most important goal. He believes it is less important to have a democratic-socialist president than it is to have people well placed further down the political spectrum, effecting change from below.

He said: “Electing people like Alexandria Ocasio-Cortez might be more important for the left than for the left to engage in worrying about who’s the best candidate for 2020.”

Svart said the DSA was as interested in furthering leftwing ideas outside elected politics as inside the Democratic party.

She said: “Leaning the Democratic party to the left is not really our goal. Some of our members feel that way, [but] some of our members don’t want to really do that much for the Democratic party.

“We are enthusiastic about the fact that there is this strike wave which we haven’t seen in years.

Teachers in Arizona, West Virginia and Oklahoma went on strike earlier this year seeking better pay, and teachers’ unions are also weighing strikes in California, Colorado and Illinois. In June workers at UPS won a pay rise after threatening to strike, in August inmates staged a nationwide prison labor strike, while in September thousands of service industry workers walked out in seven states, demanding the right to unionize.

Whether or not the midterms result in a lurching of the Democratic party, it is clear that for those progressive activists working to change politics in the US, even if – in the case of Barry Goldwater – that hope comes from an unlikely source.