As the title states. Any way to determine this? I'd hate to see an incumbent run unopposed.

The Washington State Public Disclosure Commission:  WA PDC Homepage

Below the orange-ish/yellow-ish "Browse" button is a field where you can search by campaigns in your area.  There are several other search options if you click the "Browse" button.

NOT the most intuitive website to use (it was built by the gov't), but hopefully it will help answer your question.

ETA:  Your county elections office should also have that info, however I don't know how accessible it will be online (It might vary from county to county).  You might have to call or email.

Thank you