(CNN) It was painful getting there, but the Democratic Congressional Campaign Committee's strategy to intervene in the contentious and complicated primaries in California worked on Tuesday night and could be seen as an inflection point in the 2018 midterms should Democrats wrest control of the US House from Republicans in November.

The committee's decision to pick some Democrats over other Democrats and slam the GOP for, among many things, supporting Democratic policies stirred up liberal angst in the weeks ahead of the primary and had Republicans crying foul.

But as the dust settled on Wednesday morning, national Democratic operatives woke up -- in Washington, mostly -- confident they had scythed their way through the dense and chaotic California "jungle primary," a nonpartisan contest that advances the two leading vote-getters regardless of party affiliation, without losing any top prospects on the journey.

After months of worry and late pangs of panic, Democrats would be on the ballot in nearly all the state's 53 districts, news that is already breeding a new optimism for a fall House takeover as the general election season kicks off in the Golden State.

But before the relief, and some muted celebration, there were nerves -- and spin. Weeks before voters went to the polls, operatives were openly discussing the possibility that Democrats would be locked out of a couple of key races. It was, some said, almost a guarantee. And the blame would fall, rightly or not, on the Democratic Party and its besieged campaign arms.

The morning after, though, the picture looked much different.

"This is the best-case scenario in terms of last night's results," said Meredith Kelly, the top communications aide at the Democratic Congressional Campaign Committee, who admitted that even on Tuesday afternoon this outcome looked unlikely. "We knew we faced a real risk of being boxed out, and that is something we felt the pressure of up until last night's votes started rolling in."

It didn't come cheaply.

The committee spent millions in the California primary -- cash that now won't be there in November when Democrats make their final push in critical races across the country. But Kelly called it money well spent.

"We have set ourselves up to win multiple seats in California in November, and we wouldn't have been able to go to the final match if we hadn't gotten Democrats through," she said. "It would have been over."

The strategy was simple, in theory: Prop up certain Democrats while knocking down the second- and third-tier Republicans who threatened to take advantage of a split vote on the left and slip into the top-two.

More challenging would be the execution: Pulling it off without doing more damage to the organization's already fraught relationship with the progressive grass roots, which often criticize the committee for untimely interventions and candidate recruitment tactics, would be more difficult.

California's 48th Congressional District was perhaps the stickiest wicket. The committee angered some local Democrats in May when it endorsed businessman Harley Rouda over scientist Hans Keirstead. The decision caused heartburn in the district's well-off seaside communities, which had been pretty clearly divided between the two candidates already, and led to new accusations that the national party was overstepping its bounds.

Whatever hard feeling followed, the desired results, again, came too. Though the race remains close, it now seems likely that either Rouda or Keirstead will move on to face incumbent GOP Rep. Dana Rohrabacher in November.

The committee's tactics -- and timing -- mitigated some of the almost instinctive opposition to its involvement. In backing Rouda late, after labor groups, the Sierra Club and organizations like Indivisible, the party was able to bolster his candidacy without a creating a situation like in Texas' 7th District, where the committee's efforts to undermine a progressive candidate likely boosted her in a first round of primary voting.

Aaron McCall, chairman of Indivisible OC 48, sang the committee's praises on Wednesday morning, cheering its decision to jump in only "after following the lead of the grassroots."

"We felt like the DCCC worked as a brilliant collaborative partner to equalize a race where a decision was made too early by the CA Dems," he said, referencing the California state party's controversial endorsement of Keirstead back in February.

Rouda campaign manager Mike McLaughlin said an $800,000 cable and TV broadcast ad, which ran for two weeks, gave the campaign a boost, calling it "gasoline on the fire that helped accelerate our momentum and the coalescing (of Democratic voters and groups) around us."

At the same time they were boosting Rouda, Democrats were busy mucking up the Republican side of the race -- first by running ads against Republican Scott Baugh, who was viewed as the biggest threat to finish second behind Rohrabacher, then by boosting Republican John Gabbard, a veteran and businessman, in an attempt to fracture the district's Republican vote.

McLaughlin called the nearly $2 million shelled out by the Democratic Congressional Campaign Committee to split Republicans "incredibly helpful" and key to stemming a top-two lockout.

"The negative Baugh spending worked," he said. "Baugh was in third place, and then the spending came against Baugh late. That started at the same time as our pro-Harley spending. So Baugh's Election Day results trickled off -- he had an OK position in the early vote, then trickled off to go into fourth place, which was the exact opposite of our trajectory."

Meanwhile, in California's 39th Congressional District primary, the committee boosted Gil Cisneros, a veteran and lottery winner, and it also spent over $2 million against Bob Huff and Shawn Nelson, two of the insurgent Republicans who could have boxed Democrats out in the district.

The strategy worked and Cisneros, according to CNN's projection, will move on to a general election contest against Young Kim, the Republican who finished first in the primary.

The party used a similar tactic in the nearby 49th Congressional District, where the committee aired ads -- to the tune of $1.6 million -- against California Assemblyman Rocky Chavez, a Republican, for voting with Democrats in the legislative body.

The ads caused plenty of consternation from Republicans, who accused Democrats of slamming their own policies. But once again the results were there. Chavez finished way back on Tuesday and CNN can project that at least one Democrat will advance to the general election in November.

If Rouda holds on to his lead in the 48th District, the committee will have emerged from the day with all nine of its "red to blue" candidates on ballots Tuesday intact and ready to challenge Republicans in November.

Should Rouda win, the group has gone 19 for 20, to date, with its preferred campaigns advancing in states like Arkansas, Texas, Ohio, North Carolina and -- on Tuesday alone -- Iowa, New Jersey and New Mexico, where highly touted hopefuls like Abby Finkenauer won in the Hawkeye State's 1st Congressional District. Andy Kim, in New Jersey's 3rd, is now set for what's expected to be a feisty showdown with GOP Rep. Tom MacArthur.

Though Democratic complaining reigned going into Tuesday's primaries, few are able to complain now, and those who are might have trouble finding Democratic voters inclined to listen.

Even Keirstead, the Democrat who saw the committee spend against him in his race, admitted that the decision to knock down Baugh in the campaign "worked for the party."

That said, as he finds himself in a neck-and-neck fight with Rouda to move on to the general election, Keirstead appeared clearly irked that the committee got involved in his side of the race.

"It was a risky thing to do, in retrospect," he said of the committee's endorsement of Rouda. "I am not sure it worked, and if they didn't do it, I would certainly be in second place."