Did George W. Bush have coat-tails in 2004?
If McCain or Romney win in 2008, it will be by too thin a margin to have coat-tails.
In a POTUS election for acompletely NEW administration:
Ike brought in a GOP majority in ‘50
Kennedy won the DEMs a clear majority in ‘60
Johnson kept the DEM majority in ‘64
Nixon gained seats for the GOP in ‘68 (althought DEMs in control)
Carter gained seats for the Dem majority in ‘76
Reagan won a GOP majority in ‘80
Bush 41 stayed even in ‘88
Clinton gained DEM seats in ‘92
W is the anomoly; In ‘00 he was elected but lost the GOP majority.
Point being - Coattails do occur