It is vanishingly rare in public life for a male and female figure to behave similarly and the man receives more criticism than the woman. The opposite is almost universally true. But in terms of the current bare majority in the Senate, Joe Manchin has been everyone's favorite whipping boy (deservedly so! he's terrible!) even though Krysten Sinema is arguably worse and at the very least as culpable as Manchin for preventing desperately needed structural reforms.
The recent in-depth interview with Sinema in which she reveals (tellingly) that her office in Tucson is unoccupied sheds a lot of light on one of the most confounding aspects of the obstructionist legacy she and Manchin are building. Any read, even a favorable one, of this interview makes it perfectly clear that this person could not give a shit about anyone or anything but her own career. Being a Senator is meaningless except inasmuch as it might give her a the right springboard into whatever lobbying job she's dying to get. This is a line on a resume. There's no signature policy she wants to enact, no legacy she wants to leave behind – this is the Millennial politics of the near future. Sincerity doesn't even need to be faked and the question "What's in this for me?" does not refer to one's odds of reelection.
This is the fundamental issue with Manchin, and apparently with Sinema as well: it is impossible to figure out what it is they want. If they wanted something then some kind of political deal would be possible. Recall some of their predecessors: Robert Byrd using his Senate seat as a cudgel for beating West Virginia pork out of his colleagues, or Carl Hayden openly boasting about trading his vote on Civil Rights legislation for Federally-funded Arizona water projects. With this current pair, it's unclear that handing them a blank check would accomplish anything. What do they want? What's their strategy? What are they hoping to gain from being the reluctant members of a bare-majority coalition?
The answer is nothing, and that is a big reason that they are so nearly impossible to deal with. They don't want anything except to play this character that they believe will pay off for them, personally, down the road. When Manchin is Governor or a mouthpiece of the coal industry and Sinema has taken her exhausting narcissism to the Chamber of Commerce or whatever, they'll look back on what they did as a success. The politics of Congress is predicated on the assumption that each individual member wants something that either benefits their constituents directly or increases the member's odds of reelection. In Manchin's case the latter is argued, although not entirely convincingly (would West Virginians really be furious if the minimum wage went up? Seems unlikely!) whereas Sinema doesn't even seem to care about getting re-elected. If they don't want anything, how can you negotiate with them?
Imagine a soccer team where two members aren't interested in scoring goals or winning the game; they're just hoping to get noticed to get lucrative jobs in something ancillary – broadcasting, modeling, coaching, acting, whatever. Not gonna win many games that way, are you? If you can't move them with "Hey, we can't win unless you do something" because winning isn't of interest to them, finding an alternative basis for negotiations is going to take some imagination.