The holiday party marathon staggered to a finish over the weekend, a final chance to be merry and bright before the obligatory joyous celebration with the relatives. "We've been out every night for the last week and a half," said a jolly Jack Kemp at Thursday's open house at the Spring Valley home of Patricia and Dick Carlson. The party was fanny-to-fanny with 240 festive folk (mostly Republicans, a few Democrats) like pundit Tucker Carlson, former Senate candidate Jack Ryan and lawyers Boyden Gray, Bob Bennett and Joe DiGenova. "Merry Christmas!" DiGenova boomed. "I refuse to say 'Happy holidays.' " And, in case we didn't get it, he led his tablemates in a rousing rendition of "We Wish You a Merry Christmas."