French Prime Minister Raymond Barre made a last-minute appeal to government supporters to vote in today's parliamentary runoff elections to ensure that the leftist opposition does not squeak through with a victory

The government is haunted by memories of the 1967 National Assembly elections in which its forces did very well in the first round of the elections but wound up with a majority of just one seat in the runoff.

Many government supporters did not bother to vote the second Sunday.

Several leftist leaders have virtually conceded defeat in public statements. Yet some analysts say that a leftist majority of about five seats is possible if Communist and Socialist voters follow their leaders' appeal to vote for the candidate of the left - and if other small leftist opposition groups also vote leftist.

Were the left to win a majority it would mean Communist participation in a West European government for the first time since the years immediatley after World War II.

Socialist leader Francois Mitterand and Communist leader Georges Marchais have been stressing that 15 million voters cast ballots for opposition groups last Sunday, while only 13.5 million voted for government parties. The combined left, vote last week as 49.5 per cent, and government backers got 48.4 per cent.

The French electoral map is stacked in favor of conservative rural and middle-class districts. The largest vot-suburb of Paris with 318,000 inhabitants and the smallest is a Gaullist middle-class district in Paris with 56,000.

Out of the 491 assembly seats, 68 were filled last Sunday by candidates who got more than half the vote. Eight of the remaining candidates no longer have opponents.

Of the 415 remaining seats, 409 are straight duels between leftists and government backers.

In both camps, there were automatic withdrawals in favor of the candidates with the most votes in last Sunday's first-round balloting. This left 245 Socialists, 147 Communists and 20 Radicals of the Left in the running against 224 Gaullists and 203 centrists and other backers of President Valery Giscard d'Estaing.

Two particularly prominent Giscard backers - Radical Party leader Jean-Jacques Servan-Schreiber and former interior minister Michel Poniatowski, still one of Giscard's closest political counselors - seem to be in serious trouble. Both are running against Socialists whose vote last Sundary combined with the other leftist votes would defeat the two leaders.

It is openly suggested that Gaullist leader Jacques Chirac would be happy to see Servan-Schreiber defeated.Chirac has been attacking Sercan-Schreiber as the symbol of everything he rejects in the Giscardist camp, even though they are theoretically on the same side.

Assuming that the present ruling coalition is reelected, Giscard seems bound to have a difficult time with Chirac as head of the largest group on the right.

Rumors emanating from Giscard's entourage are that he would rename Barre prime minister for an interim period of a couple of months but that he might later be tempted to give the position to a relatively liberal Gaullist like Justice Minister Alain Petrefitte or former prime minister Jacques Chaban-Delmas as a counterweight to Chirac.

Giscardist strategists express interest in trying to woo the Radicals of the Left away from Mitterrand and opening to their left. They apparently want to give themselves a wider field of maneuver, to reduce their dependence on Chirac and to try to head off serious labor troubles.

The Communist-led General Labor Confederation, the country's leading union, has already served notice that it will demand immediate talks for nationwide pay raises if the present majority is reelected.

The ease with which the Communists and Socialists agreed on a joint into the cabinet. Giscard's people have been talking of the need for an statement and strategy for the runoffs after six months of Communist sniping at their Socialist allies has elicited widespread comment about Communist cynicism. It is widely reported that when one of the Socialist leaders asked a Communist how come the agreement was so easy to reach last Monday, the Communist replied, "Weve made our calculations. The left will fall short by 15 seats.