On the Fourth of July, with exactly four months remaining in the 1980 presidential campaign that is still his to lose -- rather than Jimmy Carter's to win -- Ronald Reagan provided a pretty thorough preview of just how he might lose in in November.

All last week, candidate Reagan and his campaign command were simultaneously hit with a serious attack of The Dumbs. That is the most charitable explanation for the political Gong Show that somehow converted one declined speaking invitation into four days of bad stories and public doubts about Reagan's commitment to racial justice.

Reagan, who publicly opposed both the 1964 Civil Rights Act and the 1965 Voting Right Act, can and does become indignant when questioned about the genuineness of his civil rights record.He has written movingly about Franklin Burkhardt, a black man who was the gutsy football center for Eureka College right next to a scrappy guard named Reagan. After the botching of the invitation to the NAACP convention and of the reasons for his not being able to attend, the 1980 Republican candidate for president felt compelled to proclaim publicly: "I have not and I will now write off the black vote in this campaign."

Perhaps the principal problem in the entire unhappy episode was what it revealed about the Reagan campaign's thinking. An NAACP invitation was not simply, as it was apparently treated, an opportunity to speak before a group from whom Reagan could expect to win very few votes or even good reviews. No serious political person now expects Reagan, a truly conservative Republican, to complete with Jimmy Carter and the Democrats for any significant share of the black vote in November. The votes most seriously jeopardized by Reagan's action of last week, culminating in the unfortunate naming of Earl Butz to the candidate's domestic advisory council, were those of white voters who did not oppose the civil rights laws of 1964 and 1965.

What the Reagan strategists may be overlooking is that these voters are just as fed up with high taxes and governmental waste as anybody else. Ronald Reagan will need votes from these people to defeat Jimmy Carter and to govern. You don't have to be an Archie Bunker to want lower taxes. And Reagan owns the exclusive franchise on the tax cut issue among this year's presidential candidates. Carter, who may be on the verge of becoming the first president to have more budgets than press conferences in one year, is simply not believable compared with Reagan on the tax cut question.

But some people in the Reagan campaign seem to be operating on the fatuous premise that voters should be required to choose between Kemp-Roth and Public Accommodations. That's dumb.

But no dumber than was the appointment, announced on July 4, of the Honorable Earl ("Tell you why you can't attract colored . . . because colored only want three things . . .") Butz. That's the same Earl Butz whose last appearance in a presidential campaign ended when he was effectively fired by President Jerry Ford. That same Butz was hired by Ronald Reagan after the latter's vacation in Mexico was rereleased as a "working retreat" to take some of the sting out of his not going to Miami. That same Butz was hired after countless paragraphs have been written by all sorts of learned folks, explaining that the Sun Belt conservatives who support Reagan are not 1980 Dixiecrats in Lacoste shirts and Bass Weejuns.

Butz was only one of four former Ford Cabinet members who were announced last Friday as members of the Reagan advisory group, but he turned out to be the only one who had been 1) asked to leave the Cabinet and 2) recorded giving his thoughts on urban political strategy ot Sonny Bono and Pat Boone in 1976.

Perhaps what all this serves to remind those who watched Reagan decimate his primary opposition is that it is now 10 full years since Ronald Reagan has run in a general election. A fellow and his team, especially a team that has been changed as frequently and traumatically as Reagan's can get pretty rusty in a decade.