Republican leaders in Congress are very familiar with Rep. Marjorie Taylor Greenecausing them problems. But in a rare instance, she's doing it from their political left. The Georgia congresswoman on Monday night handed Democrats a significant arrow in their government shutdown quiver. She became the most prominent Republican to come out strongly in favor of the thing Democrats are demanding to reopen the government: an extension ofenhanced Obamacare subsidies. Republicans have avoided ruling out an extension of the subsidies, whichpolls show are very popular. But they've instead argued that it's an issue for another time — after the shutdown is concluded. (Democrats have countered that Americans begin enrolling in another year of health insurance next month and have said insurers must be able to plan.Studiesshow failing to extend the enhanced subsidies could cause premiums to more than double.) Greene's comments make that arm's-length approach more difficult. Raising the issue during the shutdown and accusing GOP leadership of not taking it seriously enough lend credence to the Democrats' argument that the time to have this debate is now. Greene made her comments in a meanderingpost on Xthat touched on a range of government-spending issues. She emphasized that she disliked Obamacare and even the concept of insurance as a whole. But she warned that failing to extend the subsidies would make insurance unaffordable to many Americans — including her own adult children. "I'm carving my own lane. And I'm absolutely disgusted that health insurance premiums will DOUBLE if the tax credits expire this year," Greene said, adding: "Not a single Republican in leadership talked to us about this or has given us a plan to help Americans deal with their health insurance premiums DOUBLING!!!" Greene has not said Republicans should relent and agree to extending the subsidies as part of the government shutdown debate, specifically. But it's a remarkably off-message moment for Republicans. And it's already impacting the debate on Capitol Hill. Some Democrats have taken to doing something few probably ever envisioned: approvingly citing Marjorie Taylor Greene. "Hold on to your hats," Senate Minority Leader Chuck Schumer of New York said on the chamber floor Tuesday. "I think this is the first time I've said this: Rep. Greene said it perfectly. Rep. Greene is absolutely right." Republican House Speaker Mike Johnson, meanwhile, tried to downplay Greene's criticisms. He claimed she simply wasn't aware of actual negotiations that were taking place on the issue. "Congresswoman Greene does not serve on the committees of jurisdiction to deal with those specialized issues, and she's probably not read in on some of that," Johnson told reporters Tuesday. He added: "It's implied as if this has been some sort of ignored issue. It's not been at all. Look, everybody's entitled to their opinion. Not everyone knows everything." But Greene's comments highlight the GOP's surprisingly uneasy posture here. Using shutdowns for policy concessions almost never works, because Americans overwhelminglysay they shouldn't be used as leverage. But Democrats' demand here has proved an unusually popular one. Apoll last weekfrom KFF, a nonpartisan health policy research group, showed 78% of Americans and even 57% of MAGA-aligned Republicans supported extending the Obamacare subsidies. In that way, a MAGA Republican like Greene supporting them isn't all that surprising. Where Greene's comments become particularly unhelpful to the GOP, though, is in how they cast Republican leaders. The implication of her comments — however well-informed — are that leaders are paying lip service to this issue without taking it seriously. GOP leaders have navigated a difficult path here. On the one hand, the popularity of the Obamacare subsidies and the possibility of huge premium increases for many Americans, including Republicans, who have coverage through the Affordable Care Act means they can't come out and say they'll never agree to extending them. So they have acknowledged they'll consider the issue and have even pointed to negotiations taking place behind the scenes. But on the other hand, holding those negotiations now risks looking like they're giving in to Democrats' demands. And it raises the next logical question: If you're going to extend the subsidies anyway, why not just do it now, when it can help reopen the government? None of it means that Democrats will prevail in this shutdown debate. But they've shown themselves to have more leverage than a lot of people appreciate — and more than Republicans had in past shutdowns when they were demanding less-popular policies like defunding Obamacare and building a border wall. That's raised at least the possibility that there couldactually be some kind of concessionhere. Greene's comments effectively highlight a problem that already existed for Republicans — while casting it in terms they probably wish she hadn't. For more CNN news and newsletters create an account atCNN.com