How Kyrsten Sinema's decision makes Democrats' 2024 Senate map tighter

WASHINGTON: Arizona Sen. Kyrsten Sinema decided to shake up the political world on Friday by becoming an independent. The former Democrat is still caucusing with the party in the Senate, so the Democratic caucus still has 51 members. Now, instead of 49 Democrats and two independents within their ranks, the caucus has 48 Democrats and three independents.

But that simple math hides a more clouded picture for Democrats and for Sinema herself. Sinema's interests are no longer necessarily the Democrats' best interests in the next Congress, and the 2024 Senate map became even more complicated for Democrats with Sinema's decision.

To be clear, Sinema has always been a thorn in the Democrats side during her time in Congress. Over the last two years, Democrats have had to almost always make sure that any bill or nomination had Sinema's support to have any chance of passing. That's the math when you have only 50 Senate seats in a 100-seat chamber. A lot of bills and nominations were never voted on without Sinema and Manchin's backing.

From 2013 (Sinema's first term in Congress) to 2020, Sinema voted against her party more than almost any other member of Congress. She stayed with the party about 69% of the time on votes where at least one half of the Democrats voted differently than half of Republicans. The average Democrat voted with their party about 90% of the time on these votes.

It's quite possible that Sinema's percentage of sticking with the party will lower now that she is an independent. Consider the example of former Sen. Joe Lieberman. The longtime Democrat won reelection as a third-party candidate in 2006, after losing the Democratic primary to a left-wing challenger (the now fairly moderate Connecticut Gov. Ned Lamont)

Relative to the average Senate Democrat, Lieberman voted with the party 10 points less of the time after becoming an independent than he had in his last term as a Democrat. If that happens with Sinema, she'll become even more conservative than West Virginia's Joe Manchin (the most conservative member of the Democratic caucus).

This would make sense because the incentive structure is now very different for Sinema. Ahead of a 2024 reelection campaign, she no longer has to worry about winning a Democratic primary. Sinema has to worry about building a coalition of Democrats, independents and Republicans. That is far more difficult to do if you're seen as too liberal.

This Bay News report is based on originating coverage from CNN.