The simplest explanation for this is that the 'Republican' Party is trying to protect a massive election tampering operation. The conviction is for tampering in the 2002 election. Most likely the 'R'NC is paying Tobin's bills as a bribe to keep him quiet about tampering in the 2004 election, and/or about more extensive tampering in 2002, 2000, or whenever. And probably the 'R'NC wishes to remain able to tamper with future elections.
I agree with Mark Crispin Miller that election tampering is now the overriding function of the 'Republican' Party. And it is funded by criminal operations. Even what is visible to us involves tampering paid for in large measure by crime—for example malicious (and illegally gerrymandered) Texas Congressional redistricting achieved by electing a 'Republican' state legislature using illegal campaign contributions. Of course also the DHS was deployed against Democrats trying to stop the tampering, which is an astounding fact.