The two island of civility in the ocean of calumny and cliche that is the 1980 presidential campaign are populated by Walter F. Mondale and George Bush and their respective vice presidential entourages.

The very existence of these two traveling courts is one of the best-kept secrets of the year. But journalists who stumble across them, as I did with Bush in Michigan and a bit earlier with Monday in Illinois and Iowa, know instantly that they have entered what are -- by 1980 standards -- blessed realms.

Life is not leisurely. Neither the incumbent No. 2 man nor his would-be successor is keeping the gentleman's hours that made, say, the Henry Cabot Lodge campaign of 1960 a happy rest cure for frazzled reporters.

Quite the contrary. On the typical day, Mondale and Bush will make more speeches, give more interviews and see more people than their running mates. But, perhaps, because they are No. 2 and perhaps because their personalities are different from their principals, they seems to do their work in a more relaxed, civilized manner than the big shots.

Mondale has time to kick off his shoes and have a hamburger and beer with a handful of reporters covering him. Bush wanders around a hotel restaurant, jollying the patrons and challenging friends with such political trivia questions as the name of Eugene McCarthy's vice presidential running mate when he ran as an independent in 1976.

On the stump, both men can sound the required battle cries. Mondale tells a black church audience in Chicago, "Ronald Reagan is to the American worker what Colonel Sanders is to the American chicken." Bush tells a television audience here, "What burns me up are the outrageous charges that they are making in their effort to distort Gov. Reagan's proposals and destroy his candidacy."

But they also play their audiences for laughs, and they seem to be enjoying the campaigning themselves. Mondale has built a wonderful stand-up comic routine out of Reagan's flip-flops. It winds up with the line, "My father was a Methodist minister and he once told me, 'The only trouble with deathbed conversions is that, occasionally, they get well.'"

Bush is the master of self-deprecation, telling a youngster who had surprised him with a question on the Equal Rights Amendment, "Amy, I wish I hadn't called on you. I support it. Gov. Reagan does not. And I support Gov. Reagan."

Somehow, their effectiveness does not seem dimished by their evident good humor. Mondale is the main rallying point for Democrats who are doubtful about Carter. Ed Campbell, the Iowa Democratic chairman, introduced Mondale as "the great ecumenist of our party, our own Pope John." He is being credited with swinging Wisconsin from Reagan to Carter by the work he did last week with farmers, unionists and dissenting liberals.

Bush plays a similar role on the Republican side, with his appeal to the ticket-splitters, independents and moderate Republicans who are nervous about Reagan's social policies and international pronouncements.

At the urging of Michigan Republican, the Reagan campaign put together a statewide 14-station television network to saturate the airwaves with a half-hour "Ask George Bush" program. Similar programs have been or will be broadcast in almost all the other Great Lakes battleground states.

"The only reason most of our ticket-splitters are breaking to Reagan," said a key Pennsylvania suburban county GOP chairman, "is Bush. They figure that voting for Reagan, they'll eventually get Bush as president, too."

There is not so much a reflection on Reagan's age as it is a commentary on the future presidential viability of his running mate. Mondale, too, appears to have that potential, whatever happens in 1980.

The publicity Bush and Mondale are not getting from the national networks and newspapers is more than offset by the heavy local coverage they receive in the cities they have visited.

Both men have small but expert political staffs of their own with them, and an ever-growing list of local contacts that can be exploited come 1984.

The reason they may be so civil and cheerful is that for both of them, the fun is probably just beginning.