FRANCE AN ISLAND FLING FRANCE'S PREMIER MICHEL DEBRE LAST WEEK RUSHED FROM HUMILIATING OBSCURITY BACK TO THE VERY CENTER OF FRENCH POLITICAL LIFE . EASED OUT OF OFFICE BY PRESIDENT CHARLES DE GAULLE IN 1962 AND REPLACED BY GEORGES POMPIDOU, DEBRE HAD SEEMED PERMANENTLY RELEGATED TO THE SHADOWS LAST NOVEMBER WHEN HE RAN AS A CANDIDATE FOR THE NATIONAL ASSEMBLY IN A SUPPOSEDLY SAFE CONSTITUENCY AND, DESPITE A GAULLIST LANDSLIDE, WAS SOLIDLY BEATEN BY A LOCAL GARAGE OWNER . BUT DEBRE WAS DETERMINED TO TRY AGAIN, EVEN THOUGH HE HAD TO TRAVEL 6,000 MILES TO FRENCH-OWNED REUNION ISLAND, A TINY VOLCANIC ROCK IN THE INDIAN OCEAN, WHERE A BY-ELECTION OFFERED ANOTHER OPPORTUNITY TO RUN FOR THE ASSEMBLY . THE DOUR, FUSSY DEBRE TOOK NO CHANCES . HE FLEW TO THE CAPITAL CITY OF ST.-DENIS AND CAMPAIGNED VIGOROUSLY, HOLDING 70 MEETINGS IN THREE STEAMING, SWEATY WEEKS . AS WAS CONFIDENTLY PREDICTED, DEBRE SWAMPED HIS LUCKLESS OPPONENT 30,908 TO 7,365, PARTLY THROUGH THE REUNION TACTIC KNOWN AS THE " PROMENADE, " IN WHICH OPPOSITION VOTERS ARE SENT FRUITLESSLY FROM POLLING PLACE TO POLLING PLACE, BEING TOLD AT EACH THAT THEY ARE NOT REGISTERED THERE . DE GAULLE NOW VIEWS DEBRE WITH A MORE KINDLY EYE THAN HE DID DURING HIS PREMIERSHIP A YEAR AGO ; ACCORDING TO WAGGISH PARIS COMMENT, POMPIDOU WAS LIKE A MISTRESS WHOM DE GAULLE SAW WITH PLEASURE, BUT WHO LOST MANY OF HIS CHARMS WHEN HE BECAME LA LEGITIME, THAT IS, WIFE . IF DE GAULLE GIVES THE EXPECTED NOD, MICHEL DEBRE WILL TAKE OVER THE JOB OF PRESIDENT OF THE GAULLIST U.N.R . FACTION IN THE ASSEMBLY AND EMPLOY HIS UNDENIABLE TALENTS IN DEALING WITH THE INEFFECTIVE LEADERSHIP, POOR ORGANIZATION AND INTERNAL FRICTION THAT HAVE RECENTLY PLAGUED THE PARTY