DEAR ABBY: I am writing to you because you can reach millions of people, and there are millions who need to be reached. Two-thirds of the voting population is not registered to vote! Please, Abby, help reach those people. It is so important for everyone to get involved and to be aware of what is going on in our country.

With November elections right around the corner, this would be a great time to make a plea to the majority who are not registered and are, therefore, not voting. Think of the difference they could make. - WENDY NELSON, NORTHGLENN, COLO.DEAR WENDY: I wish you had written sooner, because the deadline for voter registration varies from state to state, and in most states, it's already too late to register to vote in tomorrow's elections.

According to the League of Women Voters, two-thirds of the voting population IS registered to vote - but a very important one-third is not.

Susan Lederman, president of the league, says: "A huge number of registered voters change their place of residence each year, which means they must re-register before they are eligible to vote. Many of them postpone or forget to re-register. Finding out how to register is as easy as calling your local election board, listed in the telephone directory under `City Hall.' "

Readers, don't put it off another day.

DEAR ABBY: Nearly 50 years ago, my husband and I "had to" get married. In order to save face with our three children, we back-dated our wedding date by three months. We've had a good marriage and raised three great kids and now have 10 grandchildren.

Our children want to give us a nice family celebration, which we will graciously accept. My husband feels guilty about the date, and I say telling them the truth now would really upset everyone, so we should just leave things as they are.

Our pastor says, "Forget it and stick with the date you originally told them, as it is not a major lie." Then he added, "Some things are better left unsaid."

I have written a letter to each of our children, to be opened after I die, explaining the situation, trusting they will understand.

May we please have your opinion? - FIFTY YEARS LATE

DEAR FIFTY YEARS LATE: I vote with your pastor. You are to be congratulated on a successful marriage that lasted for 50 years. Silence is golden, and so is this anniverary, so give yourselves an anniversary gift - your golden silence.

As for those personal letters to your three children "explaining the situation" - destroy them. Your very wise pastor gave you sound advice when he said, "Some things are better left unsaid."

DEAR ABBY: This is for "Had Enough in Wisconsin," whose husband of 40 years always introduces her with, "Meet my wife - but please don't laugh."

You may get through to this insensitive clod by introducing him in the following manner: "Meet my husband - but please don't laugh; he was much better looking when I married him."

If you print this, please don't use my name. Sign me . . . ASSERTIVE IN TEXAS

"How to Be Popular" is an excellent guide to becoming a better conversationalist and a more attractive person. To order, send a long, business-size, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada), to: Dear Abby, Popularity Booklet, P.O. Box 447, Mount Morris, IL 61054. (Postage is included.)