Traders price a 77.5% implied probability against another US sovereign downgrade by any of the three major agencies before 2027 largely because Moody’s May 2025 cut to Aa1 aligned all ratings at one notch below the top tier, with S&P affirming AA+ and Fitch holding AA+ alongside stable outlooks. Persistent deficits and federal debt above $39 trillion are already reflected in current assessments, yet no fresh fiscal shocks, debt-ceiling standoffs, or governance deterioration have emerged to pressure additional notches. Market-implied odds embed the view that baseline debt-to-GDP trajectories and Treasury demand will sustain existing ratings absent major policy shifts, while acknowledging that unresolved budget negotiations or sharper primary-balance erosion could still alter trajectories before year-end 2026.