On bridge-building

Sheila Copps has an interesting theory about NDP MPs:

Once elected, NDP members of parliament usually are harder to dislodge than your garden variety MP. With more freedom to freelance, they share with the Bloc the benefits of a parliamentary platform with no government responsibilities. Socialists usually are good constituency members who work hard in the riding and build bridges with community groups.

While "good constituency members who work hard in the riding and build bridges with community groups" sounds like an entirely fair description of the NDP's members, I have to wonder about the theory that Dippers are actually harder to dislodge. Maybe it's just my recent memory of Nystrom, Proctor, Nystrom (again), etc. in the time I've been watching Saskatchewan ridings which raises some doubts. Or maybe the phenomenon is different in the Ontario ridings more familiar to Copps - which would bode well for the Dippers in Hamilton East-Stoney Creek among others.

But it's worth asking whether there's anything to Copps' theory. Do NDP MPs in fact tend toward a higher re-election rate than other MPs? And if indeed the NDP does tend to do well in re-electing its members, have the Dippers' new additions since January 2006 developed strong enough roots in their ridings to continue the trend?