Volunteer Harriet Zoller, left, greets Jon Ossoff, a Democrat running for Congress in Georgia's 6th District, at his campaign office in Sandy Springs on May 11. (David Goldman/AP)

Democrat Jon Ossoff, whose $8.3 million war chest has made him a contender for the congressional seat from Georgia’s 6th District, is under siege. The National Republican Congressional Committee is up with ads claiming Ossoff “lied” about his national security clearance. The pro-President Trump group America First Policies is priming $1.6 million of ads about Ossoff’s national security clearance. The Congressional Leadership Fund has spots linking Ossoff to comedian Kathy Griffin — and about his national security clearance.

Republican-aligned outside groups funded mainly by large donors have swamped their Democratic counterparts, led by the Congressional Leadership Fund, a super PAC aligned with House Speaker Paul D. Ryan (R-Wis.) that has announced plans to pump $7 million into the Georgia race. The main Democratic super PAC aimed at House races, in comparison, has announced only $700,000 in spending ahead of the June 20 runoff.

The disparity in outside funding has raised alarms among Democrats, who fear that the party is squandering clear opportunities in its quest to win the House majority in 2018. A surge in grass-roots enthusiasm has swollen the coffers of candidates such as Ossoff, but with the CLF alone pledging to raise $100 million to support House Republicans, key players say outside Democratic groups must do more now to support the party’s candidates, seize on the unpopularity of Trump and his congressional agenda, and undermine GOP incumbents.

In recent special elections in Montana and Kansas, Democrats failed to counter an onslaught of funding against their House candidates, who ended up losing deep-red districts by single digits. Up next is the 6th District in Georgia, as well as a special election in South Carolina.

“The organs of the Democratic Party need to step up and backstop these candidates,” said Jeff Weaver, who managed the 2016 presidential campaign of Sen. Bernie Sanders (I-Vt.) and now runs his group Our Revolution. “The Koch bothers are playing for keeps, and the powers that be don’t want to jump in. We can win if we’re outspent, but you can’t fight nuclear weapons with pitchforks.”

Some put the blame on large donors, who have not previously been asked to give so early in the “off year” of a congressional cycle. By contrast, the CLF’s latest report revealed that it had raised $7.5 million from Jan. 1 through May 5. Seventy percent of that — $5.3 million — came as a transfer from the American Action Network, an affiliated nonprofit group that does not routinely disclose its donors.

New causes, such as an anti-gerrymandering campaign led by former attorney general Eric H. Holder Jr., who now chairs the National Democratic Redistricting Committee, have diverted the money and attention of big donors. Before Trump’s ascent, Democratic leaders had suggested for years that the redistricting that will follow the 2020 Census offered the only path to flipping control of the House. And some in the party’s base, echoing Sanders, decry “corporate” influence and the very existence of “dark” money, complicating any effort to match the Republicans.

“Democrats make it as hard as possible to be successful in the outside money game,” said Bill Burton, who co-founded the first major Democratic super PAC, Priorities USA. “The roadblocks preventing donors from wanting to engage are far more abundant. Our activists want our values to be reflected in everything we do, and that’s great — but on the GOP side, they’re not as adherent to principles.”

Many intraparty critics have focused their attention on the Democratic Congressional Campaign Committee, which has been unapologetic about expending relatively little on special elections in Kansas and Montana that it viewed as unwinnable.

In Montana, the group spent $340,000 to attack Republican Greg Gianforte; its GOP counterpart, the National Republican Congressional Committee, spent $1.8 million against Democrat Rob Quist.

A memo the DCCC issued the day after Quist’s six-point loss mocked Republican groups for spending a combined $6 million to triumph in a traditional GOP stronghold but also said it “Refused to Waste Money on Hype,” claiming that polling did not justify more of its own investment.

The NRCC has also outspent the DCCC in Georgia, according to federal reports — $6.3 million vs. roughly $5 million. But the more significant disparity has been outside the party committees.

The House Majority PAC, the leading Democratic super PAC, has announced $700,000 in spending, recently launching an ad targeting GOP candidate Karen Handel in Georgia. Other Democratic groups have reported $655,000 in spending. But the CLF has already reported spending $3 million on the race, and other GOP groups have reported an additional half-million in expenditures.

Republicans familiar with the party’s outside spending say that they have been forced to invest heavily in the special elections to prop up candidates such as Gianforte and Handel and counter the intense national interest among anti-Trump Democrats. Nearly 200,000 individuals have donated to Ossoff’s campaign, according to his most recent federal filing, helping to set a fundraising record for a House race.

“We exist to attack Democrats and to protect and strengthen the House Republican majority,” said Corry Bliss, CLF’s executive director. “This cycle, CLF is prepared to raise and spend $100 million to do just that.”

For some on the left, the gulf between Democratic investment in Georgia and in the Kansas and Montana races has fueled a theory that the party is sabotaging its liberal wing. Our Revolution endorsed Montana’s Quist and Kansas’s James Thompson, and Sanders stumped for each of them.

Sanders did not stump for Ossoff, who has often eschewed progressive politics to campaign on fiscal responsibility and “sense over nonsense.” The investments in Georgia, compared with the dance around the previous races, inspired angry commentary and columns in liberal outlets, asking whether there is a quiet effort underway to undermine progressives.

“I don’t know if it’s malice, but it’s a fundamental misunderstanding of politics in modern America,” Weaver said. “This is why they lose. In Montana and in Kansas, you had Democrats who ran way ahead of the 2016 ticket, and they had to beg for support.”

Democrats have made moves to cut off that line of criticism. This weekend, Democratic National Committee Chairman Tom Perez campaigned in South Carolina to boost the party’s candidate in a lower-profile special election taking place the same day as Ossoff’s race. On Monday, House Majority PAC, Priorities USA and American Bridge, another Democratic super PAC, announced a “congressional accountability campaign” aimed at 12 GOP-held House district, including Ryan’s. But a common defense, that getting involved would “nationalize” the races, lands with a thud among activists.

“These races become nationalized whether the party wants it or not,” said Thompson, the Democratic candidate in the Kansas election. “I didn’t necessarily want national involvement until the national GOP got involved. From the moment I was nominated they said I was Pelosi’s hand-picked candidate. I’ve never met the woman. But they automatically try to make you this ultra-liberal person you really aren’t.”

House Minority Leader Nancy Pelosi (D-Calif.), who plays a supreme role in House Democrats’ fundraising efforts, has replaced Hillary Clinton and Barack Obama as the central villain in Republican ads. Yet she has not endorsed in special elections and has shied away from openly prodding large donors to give to outside groups.

In keeping with her past practice for non-election years, she has done labor-focused events for the House Majority PAC but not other events for the group aimed at her deep-pocketed donor base.

At a news conference Friday, Pelosi lamented Republicans’ “endless, special-interest, secret, dark money flowing like black substance into the campaign, suffocating the airwaves with their misrepresentations.”

But in a brief interview afterward, she said she was not concerned by the lagging performance of the outside Democratic groups that thrive on large donations, explaining that she would “rather just grow our grass-roots support.”

“I think we have to have an accelerated pace in everything that we do, but these campaigns have had the benefit of grass-roots fundraising that is remarkable, unprecedented, and I don’t know that any outside group’s spending would have changed the outcome of these elections,” Pelosi said.

Greg Speed, a former DCCC staffer who now leads America Votes, a group that helps coordinate progressive donors and groups, said that after 2016’s losses the few major donors willing to make immediate investments focused on “resistance” efforts and on long-term, state-based redistricting campaigns.

Only recently, he said — thanks to the GOP health-care push and the special-election campaigns — are they awakening to the notion that the House might truly be in play for Democrats.

“Many donors have been conditioned to believe that the House majority was out of reach until the next decade,” Speed said. “That is no longer operational. Donors will now have to walk and chew gum. There’s a real opportunity to win the House; our ability to hold it is contingent on a successful strategy at the state level through the next redistricting process.”

Charlie Kelly, the executive director of the House Majority PAC, said that the heavy spending by Republican rivals revealed their “defensive” posture in an environment where “Trump is toxic.”

“It concerns me if we haven’t made our case and made a good attempt to help explain things to folks,” he said. “I think it’s important for folks to realize, though, these are extraordinarily difficult special elections. We’ve shown real momentum in GA-6; hopefully it continues. But there’s clearly something happening, because none of these would have been competitive in previous cycles, and we have to feel good about that.”

More than a dozen top Democratic donors who have previously given heavily to the House Majority PAC declined or did not return requests for comment. A Democratic fundraiser who spoke on the condition of anonymity to frankly describe conversations with major donors said they are not accustomed to investing heavily in House races this early in the election cycle — if they invest at all.

“There is a mentality that the bigger checks make more sense when you’re talking about Senate, president or governor,” the fundraiser said. “That is a challenge that we face all the time. I think for a lot of the Democratic big donors that we have, it’s hard to get them to write a $250,000 or a $500,000 check for one House seat in the off year in a district that is very uphill.”

The key, said the fundraiser, is patience. “If you were a super-wealthy person, do you want to give House Majority PAC a million-dollar check a year and a half before an election, or do you want to wait and see what it looks like and let your million dollars sit in your bank account for longer?”