Democrats' choices are: let an extremely unpopular "independent" run unopposed and probably lose to a Republican or turn it into a three-way race where the Republican might still win.

Nobody likes Sinema. The assumption Democrats and left-leaning independents will turn out and vote for her out of necessity is flawed. She's going to be dead weight on the ticket one way or another.

Better to rip the bandage off while they have a majority in the senate.