^^^
Index and Leavenworth are kind of cherrypicking the most similar East/West sides of that district. It's more like Google Bellevue and then East Wenatchee...
Google is in the 1st and 7th. East Wenatchee is attracting (Seattle suburban) Eastsiders. Yahoo and Microsoft have both set up their massive data centers nearby to take advantage of cheap hydro electric power.
I am sorry, but the notion that people commute over the Snoqualmie pass is ridiculous. The growth over the mountains may be driven by west siders, but they aren't commuting over the cascades every morning.