"What you do is mix 20 new senators with 80 old ones. That way you get 20 percent new blood," said William Miller, who as chairman of the Federal Reserve Board knows a thing or two about arithmetic.

"It's called," he said with a punctuating pause, "the Geritol Senate."

Last night, though, the blood was still new and nearly half of the senators-elect were honored at the Georgetown home of Oregon's Sen. and Mrs. Mark Hatfield. There were a few "old senators" (Idaho's McClure and South Carolina's Hollings), at least one ex-senator (Hugh Scott), a former ambassador (Averell Harriman), a former HUD secretary of State (Henry Kissinger).

"What do you call him?" asked Rudolph E. Boschwitz (R-Minn.) spotting Kissinger in the hall.

"What about senator?" somebody asked, tossing the question to Kissinger.

"Not until 1986," Kissinger replied, adding that's when Jacob Javits' next term will be over, and "He still plays tennis."

And Moynihan's seat?

"I'd never run against Moynihan because he's my friend. Imagine what he'd say about me it he weren't my friend?"

Both Boschwitz and fellow Minnesota Republican David F. Durenberger, talked independently of each other about the defeat of Hubert Humphrey's Democratic Farm Labor Party.

"Their leader is gone and they fell apart," said Boschwitz, a plywood and home-furnishings merchant who unseated incumbent Wendell Anerson. Known as the "Plywood King" in some quarters and "Reject Rudy" in others ("We started off selling a lot of seconds"), Boschwitz clearly wasn't writing off the old Humphrey party for good.

"They're going to be very tough competition in Minnesota," he said, adding that what happened to the Democratic Farm Labor Party could happen all over again to the Republicans.

Durenberger, who defeated Robert Short for Muriel Humphrey's seat, said, "What people really want is not ideology but candidates. This year our party just presented good candidates. Don Fraser was a good man, but just too liberal and out of tune with the times."

Sen. Howard Baker (R-Tenn.) said he is more convinced than ever that what we have today is in effect a three-party system.

"I don't think anybody can win most places anymore as a Republican or a Democrat. Independent or swing voters decide most every election. which is why there were so many upsets."

Baker thought that Jimmy Carter's abrupt dismissal of Bella Abzug as his co-chairman of the National Advisory Committee for Women may hurt him in the polls -- "everything hurts, it's another wound." But he added that knowing Abzug as he does, "I haven't the slightest criticism of a president who would fire her by remote. If I were going to fire Bella, I'd do it the same way."

Kansas' Republican senator-elect, Nancy Kassebaum, who did not support extending the deadline to ratify ERA, questioned whether Carter's handling of the Abzug matter had been as diplomatic as it could have been. As for costing him votes, "It depends on the impact of the group that resigned."

Hatfield, a co-sponsor of ERA, said he thought that Abzug's dismissal would in the long run strengthen Carter's case. "Abzug did not represent what most American women want," Hatfield said.