Gilda Cobb-Hunter is furious with fellow Democrats. A veteran social worker, civil rights activist and the longest-serving member of the South Carolina House, she is losing patience with the infighting that has stalled efforts to enact the agenda the party sold to voters.

“I am seething at how Democrats continuously revert to the circular firing squad method of governing,” she said. “I just don’t understand it. I don’t understand why we continue to do that.”

As Democrats in Washington struggle through contentious negotiations over a sweeping domestic policy proposal, many party activists and officials across the country are watching with a collective head-shake and mounting anxiety.

They see Democrats in control of the White House and Congress, yet so far unable to resolve their differences over a multitrillion-dollar infrastructure and social safety net package.

The Post’s Jeff Stein explains how Democrats want to raise taxes on the rich to pay for President Biden’s $3.5 trillion rebuilding plan. (Mahlia Posey/The Washington Post)

They see in President Biden a candidate who ran on unity but is now plagued by intraparty divisions. In House and Senate Democratic leaders, they see competing priorities and a reluctance to get their members in line.

While many Democrats say that in the end, party leaders will find a way to pass their ambitious plan, some have started contemplating a nightmare scenario, in which the talks fall apart and Democrats are left explaining to voters who gave them the keys why they couldn’t get the car out of neutral.

“We’re running out of time,” said Sean Bagniewski, chair of the Polk County Democratic Party in Iowa. “The midterms are almost here.”

Eight months after taking over the reins of government, Democrats face a major test of their ability to capitalize on a once-in-a-generation chance to expand government services that hinges on their capacity to overcome disagreements. Outside Washington, Democrats say the party’s political fate is inexorably tied to the outcome.

In this instance, Democrats cannot blame former president Donald Trump or Senate Minority Leader Mitch McConnell (R-Ky.) because they have assembled a plan designed for completion with only Democratic support.

The consequences of failure would be devastating, Democratic officials and activists said, with a recognition that overhauling policing practices and the immigration system have become all but impossible, and enacting a far-reaching voting rights bill is a long-shot at best.

Democrats have packed the rest of their priorities — battling climate change, repairing roads and bridges, expanding health care and child care, and underwriting the cost of higher education — into twin proposals that are supposed to be the centerpiece of the party’s governing agenda and backbone of its midterm campaign platform.

Having already passed the infrastructure portion with bipartisan support in the Senate, Democrats can finish the job without a single additional Republican vote thanks to the process, known as budget reconciliation, they are using to pass the spending for social programs. House Speaker Nancy Pelosi (D-Calif.) said in a letter to colleagues Saturday that the House will aim to pass both measures this week.

Clinching enough Democratic support to make the whole thing work has proved elusive, putting Democrats in battleground states on edge.

“What happens in the next week is really going to be a defining moment for him and his administration,” said Shelia Huggins, a Democratic National Committee member from North Carolina, speaking of Biden.

Asked about her level of confidence that Biden and congressional Democrats will iron out their differences, Huggins laughed.

“My faith is strong, but I’m very concerned,” she said.

Biden has emerged as something of a mediator, huddling separately with different factions in search of compromise. Some party activists urged him to dive deep into the talks in the pivotal days ahead.

House Democrats are hurtling toward a self-imposed deadline in coming days to vote on the infrastructure bill, which moderate Democrats demanded as a condition of adopting a budget framework last month that made the social policy bill possible. But absent a broad agreement on what the latter bill should look like, House liberals have promised to block the infrastructure bill favored by moderates from passage, creating a conundrum for party leaders.

In the eyes of Cobb-Hunter, such logjams are the result of broader dynamics in the party and stubborn centrists whom she singled out for culpability in the most recent round of talks.

“I think it’s because we truly are a big tent party and we want everybody to get along and we don’t have a killer instinct like the Republicans do,” she said. “Democrats just don’t appreciate power — what it takes to get to keep it and how to use it.”

In today’s Democratic Party, the 2020 election sometimes seems like a distant memory. Democrats shelved long-standing ideological and policy disagreements and banded together out of a shared sense of urgency to defeat Trump.

Many of those disagreements have since resurfaced in the current fight — from the debate over expanding the Affordable Care Act versus moving toward a Medicare-for-all health-care system, to how to balance combating climate change with protecting workers whose jobs depend on the fossil fuel industry.

“Winning a majority and governing with a majority are two different things,” said Steve Benjamin, the Democratic mayor of Columbia, S.C. “We have much more pronounced distinctions in our party than we probably have ever had.”

Beyond delivering a historic expansion of the social safety net, Democrats are trying to achieve something they set out to do from the minute they took over: demonstrate that government can work.

Failure to do that would be cataclysmic, some Democrats said, fueling Trump’s claims that the system is broken and that the Democratic establishment figures who ascended to power can’t fix it. While Trump isn’t proposing policies to fix the system he says is broken, he was able to win in 2016 by stoking anger and not offering solutions. Democrats said they worry a failed agenda in Washington would be a boost for Trump, who says he may run again in 2024, and to Republicans in the 2022 midterms.

Inaction on the domestic policy package also presents more immediate perils.

With Biden’s approval rating slipping on the heels of his chaotic withdrawal from Afghanistan and his struggles with immigration and the pandemic, Democrats in competitive races are starting to feel a drag. The antidote, many say, is a sweeping legislative victory.

“I say this to everybody out voting in Congress. You know, you didn’t get sent there to sit around and chitty chat all day,” former Virginia governor Terry McAuliffe said in an interview on MSNBC. “They have got to pass these bills. We need help in the states. We need infrastructure. Do your job and pass legislation and help lift Americans up.”

McAuliffe is running for his old job in this year’s marquee election. Polls show a competitive contest, and the nonpartisan Cook Political Report recently moved the race from the “Lean Democratic” category to “Toss Up.”

Recognizing the urgency of the task before him, Biden held a series of meetings this past week with congressional Democrats in an effort to work toward a broad agreement.

The president won praise from lawmakers for his efforts, though they did not appear to yield any breakthroughs.

“One of the things that I think is important for — and I’m trying to get people to focus on — is, what is it you like?” Biden said Friday, explaining his negotiating strategy. He said such blunt prioritization helped clinch the bipartisan infrastructure deal in the Senate.

Part of the challenge ahead lies in the fact that Democrats are trying to stuff so many long-held priorities into their package, with many arguing that this could be the last chance — for years, perhaps — to enact something on such a large scale.

While many Democrats said individual provisions, if passed, will be popular and give the party strong arguments for reelection in the midterms, they acknowledge that the package has become a hodgepodge of climate, health-care and education initiatives that many Americans have only a vague sense of.

When Democrats talk about it, they tend to single out the provisions that appeal to them and the slice of the party they represent. Pelosi has long had a diplomatic way of describing the differences of opinion in her party — which she returned to in recent days.

“We are the Democratic Party. That’s who we are,” she said. “The beauty is in the mix.”

Democrats monitoring the situation from afar described the situation differently.

“We have power, and we ­haven’t done anything with it,” Bagniewski said.