Try alamo and discount I.D 7014650 which I found on their website, Alamo sometimes has good last-minute rates. Also, their website has a "hot deals" ad up top where you can sometimes get a good 5-day rate if you stay over a Sat night. The "hot deals" section will probably also have a $20 off weekly coupon that you can also plug in.

Final update: received call from S.O.
He arrived PDX and found a line of about 20 people at Enterprise counter. He didn't want to use the above-mentioned Advantage reservation because he wanted a car from a company where he didn't have to use a shuttle (bad experience in past finding offsite parking lot to return car in the dark). He walked over to Dollar counter, was waited on immediately, given a price just $20 over the Advantage quote. Is very happy.
Thanks to all of you for advice.
gail

Wow, it is nice to know the end result of this little challenge. Glad it worked out.

Now watch out for the acid girl.