President-elect Joe Biden is expected to announce California Attorney General Xavier Becerra as his nominee for secretary of Health and Human Services in the coming days, according to three sources familiar with his plans. 

The selection of Becerra, who served 12 terms in Congress and was a member of House Democratic leadership before his appointment to replace Kamala Harris as California's top law enforcement official, comes as Biden's campaign has faced criticism from the Congressional Hispanic Caucus and Latino advocacy groups about the diversity of his future cabinet.

Becerra, who has taken on the Trump administration over immigration, health care, gun control and environmental rules in over 100 lawsuits, was thought to be a potential attorney general nominee for Biden, or even a successor to Harris in the Senate next year. 

The Congressional Hispanic Caucus encouraged Biden's senior aides to consider Becerra for that post, and New Mexico Gov. Michelle Lujan Grisham for the role of Health and Human Services secretary, in a call earlier this week, where members criticized Biden's transition over leaks regarding Lujan Grisham being offered another post in the incoming administration. 

Should he be confirmed by the Senate, Becerra would take a leading role in the Biden administration's coronavirus response efforts. 

Becerra, the son of Mexican immigrants, would be the first Latino to lead the department, and the second Latino nominated to serve in Biden's cabinet, after Alejandro Mayorkas, a Cuban immigrant and Biden's pick to lead the Department of Homeland Security.

A Biden transition spokesperson declined to comment on the planned announcement. Becerra's office did not immediately respond to messages seeking comment.

-ABC News' Benjamin Siegel, Katherine Faulders and Molly Nagle.

As many Republicans refuse to accept a Biden victory, Sen. Dick Durbin, D-Ill., said the focus should be on the coronavirus relief package.

“Joe Biden is going to be sworn in as the next president," he said on ABC's "This Week" Sunday. "I hope we don’t get embroiled in that debate further."

In a separate interview, however, Sen. Mike Braun, R-Ind., refused to acknowledge Biden's election win, despite the mounting legal losses and Republican-led states certifying results in the Democrat's favor.

"We've got a process and I think we have been going through it since the election, and it's going to play itself out," Braun told ABC News Chief Anchor GeorgeStephanopoulos.

Georgia Secretary of State Brad Raffensperger said he was disappointed that Trump didn't win in Georgia, but said there's been no evidence of systemic fraud.

"At the end of the day, we as Republicans didn't turn out enough voters. Our office, as secretary of state, is really just to look at what those votes totals were, and we report the results. And that's why it gets back to the state party (that) didn't do their job, didn't raise enough money and didn't turn out enough people," Raffensperger told ABC News Chief Anchor George Stephanopoulos on "This Week." Sunday.

In a meandering, nearly two-hour speech -- speckled with baseless claims of voter fraud, misleading statements about court cases and assertions he will be serving a second term -- President Donald Trump pushed for Georgians to get out on Jan. 5 for the runoff election that could determine control of the Senate.

With 48 Democrats (and liberal independents) and 50 Republicans, wins from Sens. Kelly Loeffler and David Perdue would lock up another two years of GOP control. If their opponents, Rev. Raphael Warnock and Jon Ossoff, respectively, win then Vice President-elect Kamala Harris would cast the deciding vote.

"Georgia patriots must show up and vote for these two incredible people," Trump said. "And I'm telling you, they're two of the finest people you'll ever meet. We can fight for the presidency and fight to elect our two great senators."

Trump spoke out against Republicans boycotting the runoff, saying the "radical left" would win if that happened.

The president tied the Democratic candidates to regular conservative targets like Sen. Elizabeth Warren, Rep. Alexandria Ocasio-Cortez and even Beto O'Rourke. He also repeatedly attacked Stacey Abrams, a former Georgia governor candidate, who helped organize Democratic voters and swing the state blue.

At one point, Trump even went on a tangent saying he did not want to attend the rally and didn't like helping other people. Oddly, he never explained what changed his mind.

"David and Kelly called and said, 'Will you do a rally?' I said, 'Not really,'" Trump regaled the crowd, referring to staffers coming to him to ask about doing the rally. "I said -- when they asked -- I don't do it for other people. It's a lot of work to do a rally."

Loeffler and Perdue were finally invited on stage to speak over an hour into the president's rally. Each spoke for only a minute or two before Trump took the microphone again.

Trump then went back to discussing the alleged transgressions against him in the presidential race. He went on to show a lengthy video of right-wing news media touting already debunked claims of fraud.

There were unmistakable signs Wednesday of a growing rift in the Republican Party as allies of Trump -- still fastened to the idea that the 2020 election was rigged -- implored a large crowd of supporters to forget about the pivotal Georgia runoff elections.

Urging Georgians to make clear "you will not vote until you know your votes are secure," Trump ally Sidney Powell told a large and boisterous crowd in Atlanta to focus their energy instead on protesting officials from both parties who she blames for a global conspiracy to throw the election. The widely debunked conspiracy involving the company that makes voting machines is also the premise of her multi-state legal effort.

"There should not be a run-off, at least on Dominion machines," Powell said.

The message could not be further at odds with a national Republican drive to back two GOP candidates who were forced into runoff elections for the state's two U.S. Senate seats -- the outcome of which will determine control of the chamber.

The "Stop the Steal" rally at an Atlanta-area park also featured conservative lawyer Lin Wood, who used the platform to push baseless and outlandish claims about fraud in the 2020 election and generated a huge response with cries for a revolt to put Trump back in office.

Wood, wearing a red MAGA hat, at one point called for the Republican governor of Georgia to be locked up and urged rally-goers to protest outside Brian Kemp's house. The incendiary language came just one day after Gabriel Sterling, a top official in the GOP secretary of state's office in Georgia, made a passionate plea for civility and rebuked Trump for not condemning threats of violence against people overseeing the voting system in his state.

"I want you to go to the governor's mansion, I want you to circle it ... until Brian Kemp comes out and orders a special session of the GA legislature ... then as far as I'm concerned, lock him up," Wood told the excited crowd, which then erupted in "lock him up!" chants.

"I state as a matter of fact you are a criminal," Wood repeated about Kemp. "You need to go to jail."

Powell used similarly inflammatory language in urging the crowd to "flood" Georgia lawmakers with phone calls and letters to protest the certification of the election.

The rally in Georgia was organized by the same "Stop the Steal" group that has been protesting the election results across the country since the election, promoting baseless claims of widespread fraud and urging legislatures to overturn the results.

"Stop the Steal" is a pro-Trump group that quickly emerged flowing the 2020 election fueled by baseless claims of widespread voter fraud. It's led by popular pro-Trump social media activists and has been organizing "stop the steal" rallies around the country calling for the results to be overturned.

Sterling responded to the rally in a press conference Wednesday.

"I find it interesting that somebody who's had a Democrat voting record since 2004 is out there telling Republicans not to vote in an election," he said. "We encourage all voters to vote in an election -- Democrat, Republican, Independent, Green, socialist, you know, Libertarian, whatever party you want to be -- go out and exercise your vote because that's your right as an American."

Sterling also shot down Powell's claims about votes being switched as "not true" and noted that there was also a by-hand audit in the state. 

-ABC News' Will Steakin, Olivia Rubin and Quinn Scanlan