The Republican primary
As it stands now, DeLay is very unlikely to have serious trouble in the Republican primary. Tom DeLay won't lose this primary unless local activists and party leaders start abandoning him. To date, no one is.
As of right now, I'd be surprised if any prominent Republican officeholders in the district endorse one of DeLay's opponents. Moreover, my experience and the people I talk to tell me the activists feel the same way. I recently attended the Christmas party of a Fort Bend Republican womens group (what a reporter I am!). Nobody I spoke to was any less than 100% for DeLay.
Most Republicans will probably follow President Bush, who issued his support for DeLay and said in mid-December that he believed DeLay to be innocent. It's hard to see GOP primary voters voting against DeLay when no prominent Republicans are leading them in that direction.
There are certainly things that could shake this analysis up. If DeLay were to be indicted by the DoJ over something related to Abramoff, that would probably be a different story. Many Republicans would take a DoJ indictment much more seriously than the indictment by Ronnie Earle in Austin. Likewise, if DeLay were found guilty in Austin.
But to date these things haven't happened, so DeLay would have to be considered a very, very strong probability for victory in the primary.