Mark Russell, who opened his 19th season last night, retains his crown as congressional jester and star-spangled satirist. He should, however place a little disclaimer at the bottom of his mock-presidential podium: "These jokes may be somewhat diluted because I'm an avowed and unabashed Anderson supporter." That fact colors has stinging witticisms.

Now at the Shoreham Hotel Blue Room while his home base, the Marquee Lounge, is being remodeled, Russell continues to throw barely muted darts at familiar targets. In two decades, the titles have remained the same; only the names have changed. He must still give secret thanks to what UPI White House correspondent Helen Thomas once defined as his gag-writing team --"435 members of the House and 100 members of the Senate." The president and would-be president come in for equal abuse.

Of Carter, Russell says, "I don't know who's more embarrassed -- Jimmy about Billy's actions or Billy about Jimmy's actions. President Carter has agreed to debate -- Jacob Javits."

Reagan, whom Russell seems to loathe beyond his normally non-partisan considerations, is thus portrayed: "Marconi was still alive when Reagan was born . . . he was born six years before the Russian revolution . . . he was a teen-ager before movies started to talk . . . in his first movie, Gabby Hayes got the girl."

There are swift and well-placed kicks at political conventions, Abscam, defense budgets, Dominique's ("They'll strangle Bambi at your table over there" -- the owner of the famous restaurant was in the audience). He described Muskie as "one of the finest secretaries of state we had all year." On sanctions against Iran: "We'll buy all our carpets from Sears." There was also the usual collection of Russell's satirical songs.

Russell still sounds like he's just read the news wires in his dressing room before stepping onstage. He pokes, and hypocrisies burst; he jabs, and absurdities come into focus. He even speaks well of someone on occasion: He points out that H.L. Mencken was "the only famous person from Maryland who remained unindicted throughout his career."

Mark Russell, who will appear at the Shoreham through Oct. 31st before outside commitments start breaking up his season, is still a satirist of the highest order, the one you'll never regret asking, "What's so funny about politics?" Russell's been telling the public for 20 years.