In Washington silliness knows no season, but the summer here always seems to bring out the most ludicrous in us. Sensible people flee this muggy capital built on a swamp. The rest of us, press and politicians alike, remain behind trapped in the haze, forced to take our fun where we can find it. Fortunately the past few days are rich with examples of new political foolishness.

We've had "Crispgate," the bugging -- or was it the tapping -- of the GOP courtesy of Muzak, an event that just happened to occur virtually eight years to the day after that other celebrated Washington case.

We've had further evidence that you still can't underestimate the ignorance of parts of the American public: John Jenrette became the latest in a line of congressmen facing corruption charges who was endorsed by the folks back home in an election. And now we've had another piece of truly delightful political stupidity.

On June 17 a mailing was sent out in Washington from "The Honorable John Tower," under the aegis of the National Republican Senatorial Committee. In his letter, Tower, a senator from Texas, made what he called "the most important request I will ever make of you." He added:

"I want you to help me give our country a Senate controlled by conservative, pro-free enterprise, Republican senators.We need to win just 10 seats in 1980 to accomplish this.

"I have attached to my letter a confidential memo from John Heinz telling how we can accomplish this task. I have asked John for permission to reproduce this memo and send it to a few people like yourself whom I can count on not to copy and distribute it.

"It is important that labor and liberal Democratic Party be kepy unaware of our plan until it is too late."

Heinz, another Republican senator, asked Towar to become chairman of a national finance committee. His task was to raise $2 million to be used to defeat Democratic senators this fall. Tower, in turn, was asking people to become members of his finance committee and pledge to raise $600 each in the next five months.

The Heinz memo spells out how the Republicans can take control of the Senate and fundamentally shift the balance of political power. He makes these points:

1. Private polls indicate that to retain their seats many Democratic senators up for election this year will have to run 10 to 15 points ahead of Jimmy Carter if inflation continues to rise.

2. The numbers now are working for the Republicans: in 1980 and 1982, there will be a total of 46 Democrats up for reelection. Twenty of their seats are considered vulnerable. At the same time, only 22 Republicans are up for reelection.

Two years ago, the Republicans won 20 out of 35 Senate elections. This year, 24 Democratic seats will be contested, and 14 of them are in swing or Republican states where Democrats lost five to six races in 1978. The vulnerable Democrats are Gravel of Alaska, Cranston of California, Church of Idaho, Hart of Colorago, Culver of Iowa, Nelson of Wisconsin, Eagleton of Missouri, McGovern of South Dakota, Bayh of Indiana, Leahy of Vermont and Durkin of New Hampshire.

Heinz says:

"Overall, if each party did the same in each category in 1980 as it did in 1978 the results would be catastrophic for the Democrats. They would lose 13 seats, the GOP would lose three, and the Senate would be Republican, 51-49."

3. There is a shifting mood among the electorate that places many liberal Democrats elected in the '50s and '60s in a highly vulnerable position.

Out of all this, in the Republican scenario, would could the replacement of Democratic liberals in key leadership positions in the Senate. Heinz envisions these changes:

Strom Thurmond takes Ted Kennedy's place as chairman of the Judiciary Committee. Orrin Hatch replaces Harrison Williams as chairman of Labor and Human Resources. Jesse Helms takes the place of either Herman Talmadge or McGovern on Agriculture. And Jake Garn replaces William Proxmire as chairman of the Banking Committee.

A political revolution, indeed.

Stamped across the top of the Heinz memo are the words: CONFIDENTIAL Do Not Duplicate

Obviously, such an important document must not fall into the hands of the enemy. Equally obviously, publication of it is certain to work at uniting a sorely divided Democratic Party. So how did this intrepid journalist come up with this highly confidential material? A leak from a most high and secret source? A black-bag operation in the night, complete with surgical rubber gloves? A skillful wiring of the inner sanctum?

Alas, no, it simply arrived in the mail. And the Republicans got the name and the address, and even the zip code, of the reporter correct.