The contrasting styles of Arizona's new senators seem to become clearer with every step they take.

On Thursday, U.S. Sen. Kyrsten Sinema, a Democrat, took her ceremonial oath of office using a copy of the Constitution rather than a religious book, as most members usually do.

By contrast, U.S. Sen. Martha McSally, a Republican, took her oath using a Bible recovered from the USS Arizona, which sank during the attack on Pearl Harbor in 1941.

Sinema's move, while legally irrelevant, may only heighten speculation that she is an atheist.

Vice President Mike Pence ended Sinema's oath with the usual words, "so help you God?" Sinema responded, "I do." Afterward, he noted that he looked forward to working with her in the Senate.

Officially, Sinema identifies herself as religiously unaffiliated, and is the only member of the House or Senate to do so, according to the Pew Research Center for Religion and Public Life.

A spokesman for Sinema said Sinema used a book from the Library of Congress containing the texts of the U.S. and Arizona constitutions. He did not address her religious views.

"Kyrsten always gets sworn in on a Constitution simply because of her love for the Constitution," Sinema spokesman John LaBombard said.

The website Friendly Atheist welcomed Sinema's symbolic act of religious independence.

"To be sure, Sinema isn’t an open atheist, and there were a lot of books other than the Bible this year for newly elected members of Congress" the website noted Thursday. "But it’s still nice to see a government official show people that her allegiance is to our country and our laws, not a holy book or the Ten Commandments. Sinema did the same thing in 2013 when she was first sworn into Congress."

McSally's choice for her oath was in keeping with her public persona as well. McSally, a former combat pilot who frequently mentions her faith, noted the Bible's origins to Pence, who was surprised and announced it to onlookers.

"Pretty amazing," McSally said. "How special is that?" Pence responded.

Her office later put out a statement about the pocket-sized copy of the New Testament.

"The Bible was loaned to Senator McSally for the occasion by the Special Collections department of the University of Arizona library. It was recovered from the body of an unidentified sailor after the Dec. 7, 1941 Japanese attack on Pearl Harbor," the statement said.

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