Should I leave out a degree on my resume? [View all]

I earned a PhD 15 years ago. I taught as an adjunct for a couple of years while I applied for every opening I thought I was remotely qualified. I had two interviews and no offers.

Meanwhile, a full-time opening that required one of my masters degrees opened up and I took it. I've been working in this field for some 14 years now but feel for a variety of reasons it's time to move on. I thought I would stay in my alternate career as I have from time to time applied to openings requiring my PhD, without success. A college or university is simply not going to consider a 50+ year-old who last taught 14 years ago, so I have to stay with my alternate career.

My question is: the openings I'm looking at require a masters only--which I have--but not the PhD. I thought I'd make myself more "marketable" by omitting reference to the PhD on my resume.

Advice?