He was just too close to Abramoff, and thats not good for Delay's future in politics.
That may well be when it's all said and done.... But the event that has him out of the ML position is his indictment in Texas. DeLay and his attorney tried their damnest to get it squash or thrown out but was unsuccessful. Since Delay was unsuccessful in that attempt he was leaving the House with a Temp ML if he tried to hold onto his title. Other reps began to search for the 50 needed signatures to hold an election to replace him with someone permanent. Once that started and DeLay new he couldn't get a quick resolution to his Texas indictments I think he took the correct course and is stepping down.
Now the Abramoff thing may well hold a lot of problems for him and others, but it maybe a good while out before any legal actions are taken. Just my opinion and obviously yours differs as is your right.