Sorry for the late reply, but I did not have time/energy before the trip to provide an update. I was finally successful at $170 with the Renaissance Mayflower for 3/14-3/16 using Priceline. Started at $60 and upped by $5 each time, adding/including Dupont Circle in the bidding as suggested above. As it turns out, the Mayflower is fairly convenient to Dupont Circle (only about 2-3 blocks, easily walkable). Metro is very close (red line less than 1/2 block, essentially running under the hotel) and orange/blue lines within 3 blocks), so the stay worked out pretty well and the hotel/service were very good. The next two nights (3/16-3/18) were spent at Embassy Suites Convention Center, booked through Hotwire. While it was a little further from the Metro, it was still a convenient/good location, and the hotel/service were quite good (especially the free cooked-to-order breakfast and nightly manager's reception). Thanks to BetterBidding for providing the variety of information for Hotwire and Priceline.