We forecast adjusted leverage at Summit Midstream Partners L.P. (SMLP) to remain above 5x through 2021. As a result, we are lowering its issuer credit rating to 'B+'. The outlook is stable. At the same time, we are lowering our issue-level ratings on Summit Midstream Holdings LLC senior unsecured debt to 'B+', reflecting our expectation of '4' average (30%-50%; rounded estimate: 30%) recovery in the event of default. We are also lowering the preferred stock rating to 'CCC+' from 'B-'. The 'B-' issuer and issue-level credit ratings on Summit Midstream Partners Holdings LLC (SMP Holdings) are unchanged. The stable outlook on SMLP reflects our expectation that it will maintain adequate liquidity and stable operations over the next 12 months. We