These same credit rating agencies had a large role in the financial crisis due to how they over-rated mortgage-backed securities. I'd take anything they say with a heavy grain of salt.
The 2011 debt ceiling crisis was also entirely the Republican's fault. Before, raising the debt ceiling was always a matter of course, just like presidents signing budgets that had been unanimously passed through Congress was always a matter of course. But Congressional GOP members decided it wise to try and hold the government hostage, refusing to pay for things that had already been voted on and passed. They claimed it was because they were concerned about deficit spending and were demanding cuts to certain programs they didn't like, but, as pointed out above, this was beyond stupid as this pointless brinkmanship ended up raising the interest rate the US was paying, costing them way more.
Democrats have used the debt ceiling in the past for political maneuvering, but they were never dumb enough to let it go so far that it resulted in a credit downgrade for the country that we'd be paying for for decades.