Come next January, even veterans of the Annapolis scene are going to need a scorecard to keep all the new players straight.

Just consider the changes that a once-in-a-generation election year will bring: a new governor; a new House speaker to replace Benjamin L. Cardin, who is running for Congress; a new Senate president to replace Melvin A. Steinberg, who has joined the gubernatorial ticket of Baltimore Mayor William Donald Schaefer, and a large group of new committee heads to replace those who lose out in the shuffle for new presiding officers and those who retire or lose at the polls.

Steinberg's decision to run for lieutenant governor has removed the one element of stability that had been expected to carry into 1987. The loss of Steinberg after one term as president means that members of both the House and Senate will face leadership struggles over the summer.

In the Senate, the leading candidate to replace Steinberg is Democratic Sen. Thomas V. Mike Miller, the head of the Prince George's County delegation and chairman of the Judicial Proceedings Committee.

But the election will not be automatic or uncontested. Already, Sen. Laurence Levitan, a Montgomery County Democrat who chairs the Budget and Taxation Committee, and Democratic Sen. Norman R. Stone Jr., the Baltimore County chairman of the Economic and Environmental Affairs Committee, have expressed an interest in the presidency.

Steinberg has said publicly that he hopes his leaving will not spark a political bloodbath among those hoping to succeed him. That is a somewhat curious message coming from Steinberg, whose 1982 battle to topple Sen. James Clark was a street brawl of epic proportions.

On the House side, Steinberg's decision to run with Schaefer has made Del. R. Clayton Mitchell Jr. (D-Kent) the odds-on favorite to become the next House speaker. Not a bad consolation prize for the Eastern Shore Democrat, who had hoped to run with Schaefer.

Should Mitchell and Miller take over the General Assembly leadership, it would be the first time since 1978 that both the Senate president and House speaker come from outside the Baltimore area.

In the House particularly, the impending changes go far deeper than just a new speaker. For the small band of Republicans, 1987 will bring new leadership to replace Minority Leader R. Robert Neall, who is running for Congress, and assistant minority leader Lewis R. Riley, who hopes to move up to the state Senate.

In addition, some committee heads will not be returning. Constitutional and Administrative Law Committee chairwoman Helen L. Koss (D-Montgomery) announced this week that she will retire rather than run for another term in the House. There are persistent rumors that Economic Matters Committee Chairman Frederick C. Rummage (D-Prince George's) will also retire, perhaps to become a lobbyist. And if Mitchell becomes speaker, his post as Appropriations Committee chairman becomes vacant as well.

Perhaps nothing better illustrates the winds of change coming to Annapolis than the outlook for the House Ways and Means Committee, a key panel that shapes tax policy and that historically has provided some of the assembly's most influential members.

Many of the most senior members of Ways and Means will not be returning next year.

Vice Chairman Gerard F. Devlin of Prince George's was recently appointed to a District Court judgeship, which he described as "every Irish boy's dream -- going from one public payroll to another without interruption."

Del. Lucille Maurer (D-Montgomery), the legislature's preeminent expert on public education funding, is running for state Senate against another Montgomery County Ways and Means veteran, Democratic Del. Idamae Garrott.

Baltimore County Democratic Del. Thomas Kernan is running for County Executive in his home county. Democrat Dennis McCoy of the city of Baltimore has chosen to retire. Ida G. Ruben of Montgomery and Albert R. Wynn of Prince George's are running for State Senate. And former Democrat Thomas J. Mooney of Prince George's is running for governor as a Republican.

What all these changes probably mean is that 1987 will be an unpredictable year in Annapolis, a year for a new cast of characters to feel each other out as they get comfortable with new relationships.