Besides the brazen abuse of authority it would represent, the politics could also backfire badly on the administration, as Ezra Klein points out:
If testing the question wouldn’t cost anything, there would be no harm in trying. But I don’t think it would have no cost. The strength of the Biden administration’s political position is that it stands for normalcy. The debt ceiling has always been raised before, and it must be raised now. But if the administration declares the debt ceiling unconstitutional, only to have the Supreme Court declare the maneuver unconstitutional, then Biden owns the market chaos that would follow. Who will voters blame in that scenario? Republicans, who say they just wanted to negotiate over the budget, as is tradition? Or Biden, who did something no other president had done and failed?