Fortunately, I easily got through on the elite line. I had learned that there is a United flight that is almost the duplicate of our original Continental SEA-EWR leg - it just leaves a little earlier. We managed to get on that flight, except in coach instead of in first class like we were on the original flight. We had gotten the first booking as a Saver pass, and the equivalent was evidently not available on the United flight. (Although the seating chart shows only one 1st cabin seat taken.) I am still happy to have the travel day simplified, if a little miffed at the downgrade.