Sen. John Thune endorses Arizona GOP Senate candidate Kari Lake

Following Sen. Kyrsten Sinema's, I-Ariz., announcement that she won't seek reelection, Arizona Republican Kari Lake picked up the endorsement of Senate Minority Whip John Thune, the No. 2 Republican in the Senate, ahead of a fundraiser she hosted Wednesday night in Washington featuring 17 Republican senators.

"Thank you to Senator Thune for the endorsement," Lake said in a statement to ABC News. "He worked to confirm President Trump's judges and pass his agenda. I am looking forward to doing that when we win Arizona and secure the Senate majority."

Lake has now secured four out of six endorsements from the Senate Republican Leadership Conference as she seeks to shore up credibility she lost disparaging the late GOP Sen. John McCain during her losing gubernatorial run, a race she says was "stolen," a claim that failed repeatedly in court. She is also a 2020 election-denier, repeatedly claiming, like former President Donald Trump, that the presidential election was rigged.

Thune, in a statement shared with ABC News via Lake's camp, called her race "critical" as Republicans seek to win back the Senate.

"The Senate race in Arizona is critical for securing a Republican majority in the Senate. Kari Lake is the candidate in Arizona who will work to get the economy back on track and lower the cost of living for families, secure the border and enforce the law and bring safety to our streets," said the South Dakota senator. "A vote for her opponent is a vote for (President) Joe Biden's dangerous agenda. I am excited to endorse Kari Lake for Senate in Arizona."

With Thune's endorsement of Lake, the South Dakota senator appears to be aligning himself closer to Trump, whom he's criticized in the past.

In 2020, Thune was against the former president's efforts to delegitimize the 2020 presidential election. Thune notably said those attempts would go "down like a shot dog." More recently, Thune voted in favor of the bipartisan national security supplemental despite pressure from Trump to reject it.

But last week, Thune endorsed the former president -- a week before announcing his own run to replace outgoing Minority Leader Mitch McConnell in the top spot.

"I worked closely with him when he was president last time. You know, I was one of the key negotiators on the Senate Finance Committee on the tax cuts and Jobs Act," Thune said on Feb. 29. "We put through, I want to say, 150 judges when I was the whip on the floor under his administration, and so yeah -- we've got a record of accomplishment, of getting things done for the American people."

Lake has also won the backing of Sen. John Cornyn, who will run against Thune to be GOP leader.

She still lacks the support of McConnell and Sen. Shelley Moore Capito of West Virginia, vice-chair of the Senate Republican Conference.

"Frankly, we need to get that old bat Mitch McConnell out," Lake said October 2022, at a rally in Queen Creek, Arizona. "They call him Senate Majority Leader. I don't see any leadership coming from him."