April is the cruelest month for poets, hockey and basketball playoff losers, and prococious high school seniors rejected by the college of their choice. But it is a precious time for presidential hopefuls.

After three months of virtually nonstop travel and campaigning, they have a chance to catch their breaths, clear their minds of the sound of their own voices, and go home for clean laundry.

The April 1 election is the lightest of the pre-convention year, with only two primaries and a handful of caucuses.

Louisiana votes this Saturday, in a race that is virtually guaranteed to produce one more victory for Republican front-runner Ronald Reagan and for President Carter.

On April 22 comes the big Pennsylvania primary -- looming as a major test for Carter and his dogged Democratic challenger, Sen. Edward M. Kennedy, and for Reagan and his closest pursuer, George Bush. Rep. John B. Anderson, the third man in the GOP race, is not on the Pennsylvania preference ballot but is seeking write-in votes and delegates.

There are first-round delegate-selection caucuses on April 7 for Oklahoma Republicans, on April 12 for Arizona Democrats, on April 17 for Idaho Democrats, on April 22 for Missouri Democrats and for both parties in Vermont, and on April 26 for Michigan Democrats.

But after what they have been through, the survivors in the 1980 presidential cast look on that schedule as a breeze.

The landscape is littered with the bones of victims of the January, February and March gyrations in public opinion, Republicans Howard H. Baker Jr., John B. Connally, Bob Dole and Philip M. Crane have withdrawn or ceased campaigning, and so has Carter's other Democratic challenger, Edmund G. (Jerry) Brown, Jr.

For all the ups and downs of the past three months, the race is reaching the Easter break just about where the opinion polls last January said it would.

Reagan was the first choice of Republican voters in a Gallup Poll published Jan. 6, drawing 40 percent of the votes with former president Ford included in the list of options, and 47 percent with Ford out.

Carter led Kennedy, in a Gallup Poll taken at the same time, 51 to 37 percent.

The last delegate counts confirm their favored status for nomination.

In the Republican contest, with 998 votes needed for nomination. Reagan has 398, Bush 72, Anderson 56, and 63 are scattered among other candidates or uncommitted.

In the Democratic fight, where the magic number is 1,666, Carter had 848, Kennedy 445 1/2, and 24 1/2 are scattered or uncommitted.

So anyone who bet the nomination fights on the basis of the January polls and went off on vacation for three months would have come back today to find his wager looking safe and the political world seemingly unchanged.

But the mythical vacationer would have missed Bush's Iowa flirtation with "Big Mo"; the drama of the Nashua debate, where Reagan used four other Republicans to upstage and embarrass Bush; the sudden emergence of "the Anderson difference"; the crash of fallen idols Baker and Connally, and the recurring discovery that lots of Republicans, a good many independents and even some Democrats will vote for Ronald Reagan.

On the Democratic side, the vacationer would have missed the slow unraveling of the Kennedy myth by the voter disapproval registered in Iowa, New Hampshire and Illinois; the flickering resurrection of the dream in Massachusetts, New York and Connecticut; and the final frustration of Kennedy's efforts to join the debate with a president who has yet to make his first acknowledged campaign speech outside the White House.

Perhaps because they are so eager for a breakthrough, most of the remaining challengers are still going through the motions of a campaign this week. Kennedy is stumping in Pennsylvania before flying to his mother's home in Florida for the Easter weekend.

Anderson launched his campaign for the District of Columbia primary last night, and kicks off his Indiana effort today. Bush flies to New Orleans today to try to capture one congressional district from Reagan, before going home to Houston for a rest.

Reagan is relaxing in California until Monday, when he leaves on a four-state, four-day swing. Carter is at the White House, but his family surrogates, wife Rosalynn, son Chip and mother "Miss Lillian," are all campaigning this week from Pennsylvania to Louisiana.

It's hard to break the habit, even when there is a break in the schedule.