You know what the "Gephardt rule" was? Majority House Democrats back in the 1970s automatically linked the debt limit to the deficit that Congress passed, so that there didn't need to be a separate vote. Then when Republicans took control of the House in 1995, they scrapped it.
And then when Democrats regained control in 2007, and had unified government with (briefly) 60 Senators in 2009, they...well, they didn't do anything at all. They didn't even pass a debt limit increase that would have at least meant that it wasn't an issue in 2011-2012 leading up to the presidential election.
Mainly, however, they failed to simply scrap the whole thing. I don't know whether they failed to anticipate that it would be a problem if Republicans took the House in 2010, or if they didn't have the votes to act because some Democratic Senators though it would be a tough vote, or if they just overlooked it entirely. Whichever: it was a clear mistake then, and they've paid for it ever since.
To be sure: one must be careful when second-guessing 2009. Remember that there were only 58 Democrats at the beginning of the historic 111th Congress, and one of those (Kennedy) wasn't always available. Not only that: intense partisan pressure to pass things as fast as possible might have upset the process that brought Arlen Specter into the Democratic caucus, giving them 60 and the ACA (and more). Still...I do think that tossing a debt limit elimination onto some law passed over those two years probably could have been done, and wasn't.