Critics of California Gov. Gavin Newsom have met the state's threshold with enough validated signatures to force a recall election of the Democratic governor this year, a contest that could land on the ballot as early as this summer or as late as December.

The recall had long been expected to qualify because it was driven by a well-organized grassroots group that gathered signatures in every county of the state -- and backed by key Republican strategists in California who brought their fundraising heft and direct mail expertise to the effort.

After largely ignoring the bid to force him out of his job, Newsom began mounting a formidable offensive to fight the recall earlier this year. But the California Democrat, who is often mentioned as a future contender for the White House, now enters a challenging new phase where he will be attempting to steer his state back to normal life as the pandemic recedes while essentially running a full-time campaign to defend his job.

Newsom's approval ratings are still above 50% and he has put a great deal of effort into accelerating Covid-19 vaccinations to speed up the state's reopening -- setting a target of June 15 for when he hopes to lift all Covid-19 restrictions. But the recall has been fuelled by anger over the restrictions he put in place to curb the spread of coronavirus throughout last year and during an alarming surge in cases during the winter holiday months. California has been one of the slowest states to get children back to school -- in Los Angeles, the second-largest school district in the country, many children did not return to school in person until mid-April, infuriating parents who worried about their own ability to work and the many hours of instruction that their students have lost this year.

In a recent survey by the Public Policy Institute of California, 53% of likely voters said they approved of how Newsom is handling his job. Only 4 in 10 likely voters said they would vote to remove him in a recall, while 56% said they would vote no and 5% are unsure.

The California governor has said that he is working as hard as he can to get children back into the classroom, and Californians back to work, while balancing the lingering safety concerns about the virus. He and his team have framed the recall as an effort by Trump supporters and right-wing extremists to wrest control of the government from progressives.

"It is what it is. This is a Republican recall," Newsom said in an exclusive interview with CNN before the latest signature tally. "An RNC-backed Republican recall of White supremacists, anti-Semites and people who are opposed to immigration and immigrants is an accurate assessment of who's behind this recall."

After the announcement, Newsom tweeted an ad on Monday tying recall proponents to extreme Trump supporters and calling it a "power grab."

"This Republican recall threatens our values and seeks to undo the important progress we've made -- from fighting COVID, to helping struggling families, protecting our environment, and passing common sense gun violence solutions," Newsom tweeted. "There's too much at stake."

Orrin Heatlie, who led the grassroots effort to gather the signatures to recall Newsom, hailed the critical milestone by noting how many people had predicted the effort would fail when it started.

"The People of California have done what the politicians thought would be impossible," said Heatlie, a retired Yolo County sheriff's office sergeant and founder of the California Patriot Coalition (who filed the petition with 124 others). "Our work is just beginning."

There are still a number of bureaucratic steps that state officials must take before the recall is officially announced -- and before Lt. Gov. Eleni Kounalakis can set a date for the question to appear before voters on a ballot. Then potential candidates vying to replace Newsom can officially file paperwork to get into the race.

For the recall to qualify, Newsom's opponents were required to gather more than 1,495,709 valid signatures from Californians by March -- the equivalent of 12% of the vote in the last election for governor -- and they ultimately submitted more than 2 million to give themselves a cushion for duplicates. On Monday, the secretary of state's office put out a new report showing that county officials have now verified at least 1,626,042 signatures as valid -- signifying that recall proponents had crossed the critical threshold.

Still, county registrars have until April 29 to continue verifying the signatures and report their final tallies to the secretary of state. After that, any voter who signed the recall petition will have 30 days to reconsider their support and withdraw their signature. State officials will then complete a second verification process to make sure there are still enough signatures to qualify.

"This now triggers the next phase of the recall process, a 30-business-day period in which voters may submit written requests to county Registrars of Voters to remove their names from the recall petition," California Secretary of State Dr. Shirley N. Weber said in a statement Monday. "A recall election will be held unless a sufficient number of signatures are withdrawn."

Weber was recently appointed secretary of state by Newsom, who had to fill the vacancy left when he sent Alex Padilla to Washington to replace Vice President Kamala Harris as California's junior senator.

Several Republicans have already announced their intentions to challenge Newsom, including businessman John Cox, former San Diego Mayor Kevin Faulconer and former Olympian and reality TV star Caitlyn Jenner. Now that recall proponents have officially crossed the threshold to qualify, the floodgates will open for dozens of additional candidates who want to raise their profiles by running to replace Newsom.

The state's voters will be asked two questions on the recall ballot. First, do they want to vote "yes" or "no" on recalling Newsom, who was elected in 2018 with nearly 62% of the vote.

The second question will ask which candidate they would like to replace Newsom, and they will choose from what is likely to be a very long list of names (candidates from different parties will appear on that same list). By law, Newsom is not permitted to add his name to the ballot as an option.

When then-California Gov. Gray Davis, a Democrat, was recalled in 2003, more than 125 candidates -- including Davis' eventual replacement, Republican Arnold Schwarzenegger -- leapt into the race, creating a circus-like political environment for months.

California Republicans, who are outnumbered by Democrats by nearly 2 to 1 in the Golden State, welcomed the prospect of a fierce campaign ahead on Monday, predicting that the recall would be supported by voters "across political parties and a range of diverse constituencies."

California Republican Party Chairwoman Jessica Millan Patterson accused Newsom of "keeping children out of school by not standing up to teachers' unions" and faulted him for dining at the famed restaurant French Laundry at a time when he was urging Californians to stay home and avoid gatherings with families beyond their own households -- an act of hypocrisy for which he has profusely apologized.

"Voters signed recall petitions because California is on the wrong track, and we deserve better than the failures of this incompetent governor," she said.

By Maeve Reston, Stella Chan and Kyung Lah, CNN