Mark Kelly sworn in by Pence, flipping Arizona Senate seat blue

Mark Kelly was sworn into the Senate by Vice President Mike Pence on Wednesday, giving Democrats a key pickup in the battleground state of Arizona — where President Donald Trump contends the election was "rigged" and the results for him and Kelly shouldn't have been certified.

Pence first swore Kelly in on the Senate floor with the state's other senator, Kyrsten Sinema, also a Democrat, holding a Bible for the occasion. Kelly was congratulated with elbow bumps by some of his new colleagues, including Senate Majority Leader Mitch McConnell, R-Ky. Then, the newest U.S. senator and the vice president took part in a ceremonial swearing-in in the Old Senate Chamber in another part of the Capitol, where Kelly, a former astronaut, was joined by his wife, former Rep. Gabby Giffords.

"Congratulations," Pence told Kelly before administering the oath of office, adding, "It's an honor for me." All three wore masks.

Kelly's twin brother, Scott Kelly, who is also former astronaut, also was in attendance for the second ceremony. He said it was "a little surreal" to see his brother sworn in.

While the remaining senators won't take their oaths until early January, Kelly's swearing-in, which reduced the Republican majority in the Senate to 52-48, took place on Wednesday because he won a special election against Republican Sen. Martha McSally, and Arizona certified the results on Monday.

Two remaining Senate races, both in Georgia, are going to runoff elections on Jan. 5.

Trump, who lost Arizona by more than 10,000 votes, maintains he actually won the state, making unfounded claims that the vote was "rigged" and blasting Republican Gov. Doug Ducey on Monday for certifying the results that paved the way for Kelly to join the Senate.

"Why is he rushing to put a Democrat in office?" Trump tweeted.

Ducey later responded on Twitter that he certified the vote because he was legally obligated to do so, and defended the state's election process as being very secure.

"I’ve been pretty outspoken about Arizona’s election system, and bragged about it quite a bit, including in the Oval Office. And for good reason," Ducey wrote.

Shortly after the swearing in, President-elect Joe Biden congratulated Kelly in a tweet, saying, "I know he’ll serve the people of Arizona well, and I look forward to working together to build this country back better."

Kelly is filling the seat formerly held by longtime Sen. John McCain, a Republican who died in 2018, for the remaining two years of his term. Prior to Kelly, Sens. Jon Kyl and then McSally were appointed by Ducey to temporarily hold the seat.

Kelly's win marks the first time since January 1953 that two Democrats have represented Arizona in the Senate.

The 56-year-old Kelly, in his first bid for public office, ran as a moderate who would be above the partisan bickering in Washington.

Kelly's wife was a congresswoman representing Arizona when she survived being shot in the head in 2011 at a constituent event. The couple founded the Giffords Foundation, which supports gun control laws around the country.

Giffords told reporters between the two ceremonies for her husband that Wednesday was "a good day — an excellent day!"