You left out one of the main things. The state govt funded PIU. The state lege, which has been controlled by GOPers for a long time, appropriated the money.
Then Perry used his line item veto power to veto the funding for PIU. But that was only after Lehmberg refused to resign. If she had resigned, Perry would have left the funding intact. And if she had resigned, then Perry would have had the authority to replace her with someone of his choice, no doubt a republican. So you would have the governor actually controlling the DA's office in Travis county.
Also, you might want to do some research on the history of who all the PIU has prosecuted thru the years. Your statement that it has been only republicans is not correct.
I totally left out the funding part, you're right, but that begs another question...why has the Republican legislature continued to fund this apparently un-Constitutional usurpation of state authority? Maybe that speaks to why Jorge Bush was so willing to sign un-(US)Constitutional bills like the creation of DHS, NCLB and the Mediscare drug benefit...he'd done it as the Texan governor in the case of the "Public Integrity" Unit.
Scouts Out! Cavalry Ho!
Ronnie Earle was Ann Richards hatchet man. He went after rats that got in her way, not as a matter of Law Enforcement but of political assassination. Republicans were expected to be targeted, but rats had better toe the line, or else!
To have Perry appoint an replacement would have been grand, as there was much swamp-draining and deadwood-cutting in such a rat infested boiler room. But, alas...