"If elected, Bilbray has 6 years seniority over Issa."
The general rule is that people who leave Congress and then return start off with 0 seniority. Sometimes the Speaker (or, if the member is in the minority, the Minority Leader) will make an exception and let the member keep his old seniority, but that usually occurs only when the candidate has been heavily recruited by the party because they need him in order to win the seat; as I've said before, I think it would be a bad idea for Hastert to give Bilbray his seniority back. But one thing that is abundantly clear is that, even if Bilbray got his old seniority back, he would *not* have 6 years of seniority over Issa, he would have 6 years of seniority, period. Since Issa was first elected to the House in November 2000 (coincidentally, the day that Bilbray lost his seat) and sworn in in January 2001, Issa has only a bit more than 5 years of seniority, so Bilbray would have a bit more seniority than Issa (and other GOP Representatives first elected in 2000) if he was elected and somehow got his seniority back, but certainly not 6 years of seniority over Issa.
I was listening to Hedgecock as I typed, and very likely erroneously combined the two statements that (1) Bilbray has 6 years of seniority and (2) per Issa's own statement, Bilbray has seniority over him [Issa}
So your correction is noted.