This is not an ASB scenario - indeed Lance Armstrong was once considered a potential candidate for Governor of Texas. Let's say he did not change his mind, and decided to retire to prepare for a future run for Governor. As a result, he did not make his so-called "comeback" in 2009, and his doping remains unknown to public for the time being. While he was seemingly friends with former president George W. Bush, he was against the war in Iraq on the grounds that it costs too much money. Some online sources say he is pro-choice.
That means he would either be a libertarian republican or just another anti-war liberal Democrat - can't really find much about his views on politics.
If he is running as a Republican, he can't possibly run for Governor or LG in 2006, though Armstrong may choose to run for a random statewide office, but I doubt if he could defeat both Perry and Hutchison in the 2010 primary.
What about removing one of the independent candidates in 2006, and have Armstrong running as an independent or even the Democratic nominee? Let's say he wins and is re-elected in 2010 as a very popular incumbent. Would we ever know about his doping at all, without his 2009 comeback that arguably produces enough evidence to kill his career? Would he be using state resources to cover up the truth?
Otherwise, if Armstrong is a Democrat, and mounting evidence of his scandal comes out just before Obama or Hillary's 2012 re-election campaign, would it be big enough to alter 2012?