Voters in eight states cast their ballots Tuesday in what amounts to the most significant primary election of the 2018 season, a Super Tuesday for partisans battling for control of Congress.

In critical races across the country, Democrats had a good night. But so too did Republicans, who avoided a disaster that could have cost them several seats in the House.

Here are the most significant results from Tuesday's electoral contests:

Dems got (almost) everything they wanted out of California

For weeks, Democrats had warned they were on the brink of electoral disaster, thanks to California's top-two primary system. If the party's bevy of candidates divided the electorate to a sufficient degree, Democrats warned, they could be shut out of races key to their chances of reclaiming control of Congress.

Democrats were closest to being locked out in Denham's Modesto-based district, where venture capitalist Josh Harder (D) held a lead of just 700 votes over conservative Republican Ted Howze for the second runoff slot. But California observers know late absentee ballots tend to favor Democrats, giving the party reason to be confident it had dodged what could have been a disastrous blow.

The one caveat Democrats now face: They might not always have gotten the candidates they preferred. In several districts, the national party's chosen candidate fell behind more progressive candidates.

But Democrats will happily take someone in the general over no one.

Republicans avoided disaster

Feinstein will likely face a fellow Democrat, former state Senate President Kevin de León, in November, though plenty of votes are left to be counted. But in the race for governor, businessman John Cox (R) secured a spot in November's general election against Lt. Gov. Gavin Newsom (D).

Cox is not going to win in a state where Democrats outnumber Republicans by an almost two-to-one margin. But the fact that there is a Republican on the ballot in the first place is enough to give Republican voters a reason to show up, avoiding a turnout collapse that could have been a catastrophe for every Republican farther down the ballot.

And two Republican women, former Assemblywoman Young Kim and state tax board member Diane Harkey, are expected to win the most votes in their bids to replace the retiring Royce and Issa, respectively. Both races will be challenging for the GOP.

The gas tax could hurt Democrats

The GOP's contingency plan, if Cox had failed to make the November ballot, is a ballot measure to repeal an unpopular gas tax Democrats in the state legislature passed last year. And Tuesday's elections offered a sign that the gas tax will be the albatross for Democrats that Republicans hoped.

State Sen. Josh Newman (D), who voted in favor of the gas tax increase in a district long held by Republicans, lost a recall election on Tuesday that will send former Assemblywoman Ling Ling Chang (R) to Sacramento in his place.

The recall campaign centered entirely on Newman's vote for the gas tax, a measure backed by Gov. Jerry Brown (D). State Democrats predicted Newman would survive, but his lopsided loss — nearly 2 in 3 voters voted to strip him of his seat — should scare Democrats in legislative swing districts.

Newman's loss robs Democrats of their supermajority in the state Senate. The party hopes to win back key seats in the general election, but for now Republicans have a foothold, however minor, in Sacramento.

Whither the liberals?

With about 4 in 10 precincts reporting, Feinstein held a strong lead over de León, 44 percent to 11 percent, with unknown Republican James Bradley nipping at de León's heels. Feinstein led the vote in every county in California.

The former state Senate president build one of the more liberal records in recent memory during his time in Sacramento, giving him a foundation from which he hoped to spring a surprise on a veteran Democrat who was slow to adapt to the changing face of the Democratic Party.

But those hopes now prove a long shot, and Feinstein begins the race to November as a heavy favorite.

"I think [de León] thought people would think that Dianne's age and her more moderate positioning gave him a real opening. And the problem with that is, if you have watched her for as long as she's been in office, the one thing you should never underestimate is her political savvy and her stomach," said Gale Kaufman, a longtime Democratic strategist in Sacramento.

But there's no sign the Los Angeles liberal is giving up. De León largely avoided criticizing Feinstein during the primary race, but in his remarks to supporters Tuesday night, he began to pivot toward his November foe.

"A majority of Californians want new leadership in Washington," de León said in Los Angeles. "In November, voters will have the opportunity to send a message to Washington, and around the world, that the system is broken, the status quo is failing, and the future is now."

De León's entrance into the race was always a gamble. He's survived the first roll of the dice, but the second roll has much more daunting odds.

Another good night for women

Democratic success in November increasingly lies on the shoulders of female candidates after another primary night in which women rolled to party nominations — in some cases by surprisingly large margins.

Both Lujan Grisham and Pearce are running to replace retiring Gov. Susana Martinez (R), the only woman of color running a state today. Lujan Grisham, the favorite in November, would take over that title if she wins.

Democrats notched another surprising win in a state legislative special election earlier Tuesday , when state Rep. Lauren Arthur (D) claimed an open state Senate district north of Kansas City. President Trump won that district by 5 percentage points in 2016.

Christina Reynolds, who heads communications for EMILY's List, the group that backs pro-abortion rights Democratic women, said women who are winning represent a diverse cross-section.

"It's a wide variety of women," Reynolds said Tuesday . "We have women who have served in state legislatures, have worked in policy and things like water rights. We have women who are coming from other offices and first-time candidates. They have proven that if you understand the district and do the work in the district, you can win pretty handily."

Finkenauer would be the youngest woman ever elected to Congress. Haaland would be the first Native American woman to serve in the House. Lujan Grisham would be the first female Hispanic Democrat to run a state. And either Finkenauer or Axne would be the first woman to represent Iowa in the House of Representatives.

A protest vote against Menendez

New Jersey Senate seats are the GOP's white whale. At times, they look so tantalizingly winnable that Republicans pour millions into last-minute ads, only to be frustrated when the Democratic machine turns out too many votes.

McCormick actually beat Menendez in six New Jersey counties — though mostly smaller counties in exurban New York and the southern shore. Menendez won on his strength in New York City and Philadelphia suburbs. But it cost the incumbent more than $3.6 million, according to the latest reports filed with the FEC.

Menendez now faces businessman Bob Hugin, who has given freely to his own campaign. Public polls show Menendez only a handful of points ahead of Hugin, raising the prospect that Republicans might invest in a state that few considered on the table as the cycle began.

The Justice Department has declined to prosecute Menendez a second time, after a jury deadlocked in his first trial. New Jersey voters seemed less forgiving on Tuesday .

—Updated at 11:52 a.m. Lisa Hagen and Ben Kamisar contributed.