A leader of Barack Obama’s historic digital election campaigns has sounded the alarm over Democrats’ failure to keep up with Donald Trump’s social media behemoth.

The US president outflanked and outspent rival Hillary Clinton on the web in 2016 and, after three years building a sophisticated digital operation with a formidable war chest, will enjoy a head start over next year’s challenger.

It is a marked reversal of fortunes from a decade ago when young liberals ruled the internet and Obama’s revolutionary approach to online organizing helped him to victories over Clinton and the Republican nominees John McCain and Mitt Romney.

Michael Slaby, the Obama campaign’s chief technology officer in 2008 and chief integration and innovation officer in 2012, said: “The difficult truth about the pace of media and technology evolution is that it doesn’t sit still so, if you’re not continuously investing, you’re falling behind, and I think there was a bit of a moment on the left of, ‘Hey, we won, we figured this out. We’re great at this,’ that gave us a little bit of overconfidence.

“There were some huge, very thoughtful and intelligent efforts on the right in 2013 to address weaknesses, catch up, do smart things and build data trust and build Breitbart and all these different projects. We have some really interesting, profoundly powerful organising groups that have cropped up post-2016 like Arena and Organizing Corps and Run for Something and Swing Left. They’re very focused on organising; I’m not saying that in a disparaging way. What they are not, though, is infrastructure.

“There is an overdue need for a reimagining and rethinking, a modernizing of the underlying infrastructure on the left that hasn’t happened yet.”

The centrality of tech to the president’s re-election effort is spelled out by his choice of campaign manager: Brad Parscale, who was digital director in 2016 and – bearded, 6ft 8in tall – is now a familiar warm-up act at Trump’s rallies. A year from the election, he is already spending millions of dollars more than Democrats to “flood the zone” of social media every day.

The Trump 2020 campaign serves up targeted adverts with often misleading messages about immigration, impeachment and other issues that would be rejected by traditional TV networks. It has mastered incendiary clickbait as a tool to pour oil on supporters’ grievances, bank their donations, sell them merchandise and absorb their data.

Washington norms are inverted online. The biggest political crisis of Trump’s presidency is translated into an “impeachment defense task force” to fire up supporters and tap their wallets. Acting chief of staff Mick Mulvaney’s recent comment to reporters, “Get over it”, widely seen as a politically costly gaffe, quickly manifested itself as a slogan on a must-have T-shirt.

Brad Parscale, Trump’s 2020 campaign manager, was his digital director in 2016, indicating the centrality of online campaigning. Photograph: Stephen Maturen/Getty Images

Some Democrats worry their response so far is analogue and anaemic. Candidates’ primary campaigns are seen as less innovative, less targeted and less ruthless about data collection and, for now at least, no match for Trump’s firepower. Former vice-president Joe Biden’s campaign has even shifted funds from online advertising to the traditional medium of TV, the New York Times reported.

The lost ground could be seen as an aspect of how, even as Obama occupied the White House for two terms, inertia set in at the Democratic National Committee (DNC) and the party endured sweeping defeats in the Senate, House of Representatives and various governerships while losing nearly 1,000 state legislative seats.

Slaby, 42, now chief strategist of the not-for-profit Harmony Labs, said: “It’s disappointing. It’s always unfortunate to lose a lead out of a lack of humility. A lot has been made about President Obama’s party-building leadership during his administration and what happened, or didn’t happen, at the DNC in that decade. I think there’s some blame there. We could have been making those investments in those years and we didn’t.

“But those investments are available to us any time. We can pick the ball up at any moment. It’s not like, ‘Oh, we missed a shot, let’s all rub gravel through our hair and blame everybody else.’ That’s not useful. But yes, it frustrates me, I think we’re missing opportunities, and ultimately I find it frustrating because it makes us less effective as leaders and that makes our civic life as a country less vibrant, and that makes me mad.”

In the past week Facebook has resisted pressure to ban political advertising, even when it contains lies, earning a rebuke from Clinton and others. Twitter subsequently announced it would refuse such ads and was met by sharp criticism from the Trump camp in turn. Concerns also persist that Facebook, YouTube and other sites could be targets of foreign interference again.

But Andrew Bleeker, who led digital advertising on the Obama campaigns, is less pessimistic about where Democrats currently stand. “I think some of the things that have led to a narrative around ‘one group is woefully behind’ or ‘dramatically ahead’ are a little bit exaggerated,” he said. “We’re sort of comparing apples to oranges in points in time.”

The Trump campaign does enjoy the hefty advantage of incumbency, he acknowledged, and can make long-term investments to build infrastructure and gather email addresses and cellphone numbers. Democrats are facing a competitive primary and so face different objectives and time horizons.

“Where I think there’s a real risk are things where time is really going to matter. It’s going to matter on the size of the audiences that these campaigns have been able to build. Trump does have a huge head start there. It’s not sophistication but the depth of his list is gonna be a real thing,” he said.

Bleeker, 34, president of communications agency Bully Pulpit Interactive, added: “There’s also the talent question and these things cut both ways. The Trump campaign, being an incumbent, has the advantage you can build a bigger in-house team or agency teams early. You have more money – he raised $125m last quarter – so you can hire whoever you want. The Democratic campaigns will hire later; they’re smaller right now on the whole.

“But on the flip side, one campaign has a larger budget from which to experiment but there are fewer groups experimenting. One of the reasons I’m optimistic about the Democratic primary is that you see a lot of good ideas in primaries. We have a lot of candidates. Only one’s going to win but there’s not only one set of good ideas and innovations. I think a lot of those innovations will make it to the Democratic nominee.”