If a single individual, aside from Howard Jarvis, the author and chief protagonist of Proposition 13, can take satisfaction from Tuesday's balloting, it is another Californian. The overwhelming passage of 13, together with the defeat of Sen. Clifford Case in New Jersey, gives Ronald Reagan a leg up for the presidential nomination of his party in 1980.

In the rivalry among Republicans, Reagan has played his cards with shrewd caution. Observing what he calls the 11th commandment - never attach a sitting Republican - he kept out of the contest between Case and Jeffrey Bell despite repeated pleas from conservatives and fund-raisers around the country.

Bell was one of Reagan's lieutenants in the 1976 presidential campaign. He is credited with having prompted Reagan before the campaign started to call publicly for a cut in the federal budget of $90 billion.

At one press conference after another, Reagan was asked where he would make the cuts if he became president. Would they be in the defense budget? Out of Social Security? His anwsers tended to be evasive, with every indication that the candidate would be happy if that $90-billion figure dropped out of sight.

But if the voters in the state where he was a two-term governor could vote 2 to 1 to cut local property taxes by anywhere from $7 billion to $12 billion, it may be that angry taxpayers are ready for a big slash in a federal budget of half a trillion dollars. Reagan can be expected to bring out some specifics matching Proposition 13, for which he voted.

Reagan and conservative Republicans in California have another reason to rejoice. Six months ago Gov. Jerry Brown Jr. was 5 to 6 points ahead in the polls of any visible Republican candidate. He seemed assured of reelection to a second term by a wide margin. On the basis of his showing in the most populous state in the union, it was being written, he would challenge President Carter in the early 1980 presidential primaries.

Now all that has changed. The latest Field poll, one of the most reliable in the country, showed Brown ahead of Attorney General Evelle J. Younger by one point. Younger nosed out former Los Angeles police chief Ed Davis for the Republican nomination for governor.

If the election were held today, according to Field, the outcome would be a dead heat, with 45 percent for Brown and 44 percent for Younger. That is a reflection of how volatile the political currents are.

Case's defeat may be an isolated phenomenon. He was running for a fifth term, and his age counted heavily against him. It was repeatedly pointed out that he would be 80 when his six-year term ended.

Nevertheless, he was one of the little band of liberal Republican senators, 14 in all, who called on President Gerald Ford in 1976 to remind him that there were those in his party who did not subscribe to Reagan conservatism. The effect on Ford was that of a feather falling on velvet as he chose a right-winger, Sen. Robert Dole of Kansas, as his running mate, sending Nelson Rockefeller over the side of the boat, and standing by as his party platform repudiated the foreign policy of Henry Kissinger.

The triumph of Proposition 13 may have much more significance than Case's defeat. At the outset of the Jarvis campaign, Jerry Brown was strongly in opposition, along with a great many officials in school systems around the state.

But as the taxpayer revolt loomed larger on the polling horizon, he spoke more softly. He is now saying that the voters of every shade of opinion have spoken, and new state income or sales taxes to make up for the serious deficiencies at the city and county level are furthest from his thoughts.

Under the amendment to the state constitution so overwhelmingly adopted, he could not raise taxes without approval by a two-thirds vote of the legislature. And anyone who believes that in the face of Proposition 13 in an election year the California legislature - any legislature - will approve a tax increase, goes to the bottom of the class.

It has long been the conventional wisdom that no one too far to the left of center or too far to the right can be elected president. On the left Sen. George McGovern, the Democratic candidate, proved that in 1972. He carried Massachusetts and the District of Columbia against Richard Nixon's landslide.

As the Republican nominee in 1980, Reagan would test the other end of the spectrum. It is hard to believe that anyone holding such consistently conservative views in both foreign and domestic policy can become president. But the tide is moving to the right so rapidly that the wisdom of the past may no longer prevail.