Has she mentioned this before and I somehow missed it?

I ask because Politico dumps this quote eight paragraphs into a longer story about her first year in the Senate, as if it’s just another data point about her quirky independent streak.

It isn’t. It’s earth-shaking potentially in its implications for American politics in the next decade — if, of course, Sinema has the nerve to stick to her guns.

Take the liberal drive to bust down age-old Senate rules in order to pass “Medicare for All” or a “Green New Deal.” Sinema not only opposes getting rid of the 60-vote filibuster threshold for legislation, she wants to restore the supermajority requirement for presidential nominees that has been weakened by both parties.

“They will not get my vote on [nuking the filibuster],” Sinema said in her office, outfitted with shiny leather and translucent chairs and boasting a vivid shade of purple that pops from the walls. “In fact, whether I’m in the majority or the minority I would always vote to reinstate the protections for the minority. … It is the right thing for the country.”…

“Everyone knows that I am very independent-minded,” she said. “And that it’s not super useful to try and convince me otherwise.”

Philip Klein grasped the significance of that immediately. There are two key questions being asked of the progressive lions, Bernie and Warren, in the Democratic primary this year. One: How will you pay for your agenda? They’ll, uh, get back to you on that. Two: How will you pass your agenda? After all, so long as the filibuster remains in place, a new Democratic president would need 60 votes in the Senate to get Medicare for All or free college tuition through Congress. And no matter how badly Republicans do next fall, they’ll have far more than the 41 votes they need to block any legislation in the event that Schumer ends up in charge of the Senate.

Bernie has been fidgety about ending the filibuster, grumbling back in February that he was reluctant to see it happen, but the simple reality is that he can’t implement socialist programs without getting rid of it. He’s begun to come around. Warren, on the other hand, has accepted it as a cost of doing progressive business from the beginning. She called for nuking it months ago. If she gets elected in 2020, it’ll be job one for the Senate.

The nice thing for Warren and Schumer is that it doesn’t take 60 votes to change the rules and end the filibuster. It only takes 51. That’s how Harry Reid was able to nuke the filibuster for non-SCOTUS executive nominees in 2013 and how McConnell was able to nuke it for Supreme Court nominees four years later. All you need is a simple majority to get rid of it. And it’s quite possible that Schumer will have that majority soon: The GOP is already speculating about a “nightmare scenario” next fall in which Trump, weakened by scandal, drags Republicans on the ballot down with him. It’s easy to envision the GOP losing five seats, with Susan Collins, Martha McSally, and Joni Ernst all being outraised by their challengers last quarter and Cory Gardner and Thom Tillis facing very tough purple-state races. Worse, Trump is raking in so much dough with the RNC that it may be cutting into the amount of cash available from donors for Collins and the rest.

Long story short, it’s perfectly possible that the Senate will land at 50/50 with Warren as president-elect. In that scenario, Democrats would theoretically have the votes to nuke the filibuster, with Warren’s VP providing the tiebreaking vote.

But now here’s Sinema claiming that she’ll provide the tiebreaking vote for the GOP. Do you see how big this is? It’s the next best thing to Republicans picking up an extra Senate seat next fall. And if Sinema’s true to her word, she would derail the entire Warren agenda. She’d allow Republicans to filibuster everything that comes down the pike apart from the narrow class of legislation that can be passed with a simple majority under the rules of reconciliation.

And best of all, it could conceivably last for the duration of Warren’s term. Sinema isn’t up for reelection to the Senate until 2024.

I don’t think she’d have the guts to be the lone holdout, though, certainly not for four years. If you think Senate Republicans are under a lot of pressure on impeachment, imagine Sinema singlehandedly obstructing the progressive program after Democrats won a landmark victory and took back government. She’d be a bigger villain to Democrats than Mitch McConnell is. She’d be primaried for sure in 2024 and, given Arizona’s blue drift, it’s plausible that she’d lose. I think she’d either cave on the filibuster after working out some sort of deal with President Warren, possibly ensuring Sinema a bit more input into the Democratic agenda, or she’d be backed up by a few other Dem holdouts, with Joe Manchin the most obvious possibility. That is, I don’t think there are any scenarios in which Schumer misses nuking the filibuster by a 49/51 margin. There may be one where he misses 48/52 or 47/53, though.