The day after Finland's presidential election last week, the largest circulation Finnish daily, Helsingin Sanomat, reprinted a Swiss newspaper cartoon depicting the countries bordering the Soviet Union as doors along a corridor. Grim-faced Soviet soldiers stood guard outside the door labeled "Iran," menacingly aimed automatic rifles at those marked "Poland" and "China" and had broken through the door labeled "Afghanistan."

But the Soviet soldier outside the door marked "Finland" was smiling and held a bouquet of flowers rather than a gun. He appeared to be waiting expectantly to court the lady inside.

This imagery aptly illustrated the importance of the election for both Finns and Western diplomatic observers interviewed here. Decisively, democratically and without diplomatic incident, the electorate conferred the considerable power of Finland's presidency on Mauno Koivisto, 59, the popular current prime minister. He also has been acting president since last October, when arteriosclerosis forced Urho Kekkonen to resign after a quarter-century as president.

The highly partisan Finns crossed over traditional party lines in a record 87 percent turnout to ensure that Koivisto's formal election to a six-year term by an electoral college that meets here today could not be frustrated by the party bosses through whom Kekkonen had manipulated Finnish politics for so many years.

According to politicians, analysts and diplomats, the voters appeared to care little about whom the Soviet Union might prefer to replace Kekkonen, whose close personal contacts with the men in the Kremlin constituted most of what mattered in Finnish foreign policy for the past two decades.

Through those reassuring contacts, plus Kekkonen's unifying and calming domestic influence, Finland evolved a politically stable and economically profitable relationship with its giant neighbor and former ruler. This greatly increased the security and prosperity of this small Nordic nation as the only freely democratic, predominantly capitalist country bordering the Soviet Union.

Perhaps most significant of all, Moscow largely avoided interfering in Finland's presidential election. There were only minor, unsuccessful attempts through articles in Pravda to persuade Kekkonen's Center Party to adopt the candidate best known to the Soviets and to prevent a split in the declining Finnish Communist Party, which instead came out of the election more deeply divided and politically weaker than ever.

"The election was an important event in the sense that the Finnish people have had a very deeply embedded fear that Russians would try to interfere in the process of picking Kekkonen's successor," said Finland's leading political and economic analyst, Max Jakobson, a former United Nations ambassador who is now managing director of the Council of Economic Organizations in Finland.

"Everyone was expecting something stronger from the Soviets," said Kari Mottola, editor-in-chief of the Finnish Institute of International Affairs. "If they believe it is necessary to protect their interests, they will do what they have to do. So they must have seen nothing here that appeared to threaten their interests . . . ."

Crises along the East-West divide, such as the military crackdown in Poland, can sometimes make the Finns feel more secure as an island of tranquillity and prosperity, a number of analysts and journalists here said.

"I don't want this to sound cynical," said Jacobsen, referring to Poland, "but it makes Finland look even better to the Soviet Union. When the Russians look at their neighbors today, nearly every one of them is bound to look bad in some way, either hostile, like China, undependable allies, like Poland or Korea, or unstable, like Iran or Turkey. Only Finland appears stable and has a stable relationship with the Soviets."

During Koivisto's several months as acting president, according to Mottola, the Soviets saw that "Finnish behavior remained low-key" concerning potentially troublesome foreign policy issues such as the crackdown in Poland and the discovery along the coast of neighboring Sweden of a Soviet submarine that appeared to be carrying a nuclear weapon.

Finland's refusal to criticize the Soviet Union over such issues is cited as evidence of a foreign policy subservience to the Soviets dubbed "Finlandization" by some American and Western European critics. Finnish officials and diplomats, who resent the term, argue they are acting realistically and in accordance with a 1948 Finnish-Soviet friendship treaty, under which Finland is to remain neutral in East-West disputes and prevent any nation from attacking the Soviet Union through Finnish territory.

"Poland is an example of the problem for Finland when there is a political dispute between the superpowers and it is not in our interest to take a position," Finland's foreign minister, Paavo Vayrynen, said in an interview. "Maybe public opinion in the United States does not understand why Finland is not joining the West in criticizing, but this is part of our neutrality."

Pointing out that Finland also refused in the past to join in criticizing the United States over Vietnam, Vayrynen added, "We are convinced that the government in Washington understands our policy of neutrality . . . ."

The American government has not been pushing Finland to take a stronger official stand on Poland, according to diplomatic sources here, because it does not believe the West would gain from having Finland's relationship with the Soviet Union jeopardized. The sources said American diplomats also have judged Finland's extensive trade with the Soviet Union to be at least as a good a deal for the Finns as it is for the Kremlin.

American diplomats have asked Finnish officials, however, whether they thought they might be overly dependent on oil from the Soviet Union, which provides two-thirds of Finland's total supply. Finnish officials answered that they were not concerned, according to the sources, but Finland has begun buying about 4 million tons of coal a year from the United States.

Rather than paying cash for Soviet oil and other raw materials, the Finns provide the Soviets with ships, engineering, construction work, clothing and other Finnish-made goods in a barter arrangement. This has meant a lucrative, job-creating increase in Finnish exports whenever oil prices go up.