Is there anything they have shown to be unable to do?
Yes, they have clearly demonstrated that they cannot balance a budget, they cannot manage a simple Ponzi scheme like Social Security, they cannot responsibly manage health care through Medicaid and Medicare, they cannot honestly collect taxes, they cannot protect our borders, they cannot effectively run [pick your favorite social program], and most importantly, they cannot follow the simplest rules laid out in the Constitution of the United States of America. Actually, the only things they can do consistently well is f**k up anything and everything they touch.