Ever since he won last September's presidential election with just 36.3% of the vote in a three-way race, Salvador Allende Gossens has been anxious to widen his slim popular margin. Last April his Popular Unity coalition of Socialists, Communists and Radicals collected an impressive 50.8% of the vote in nationwide municipal elections, and he seemed well on the way. But last week, in a by-election in one of the largest of Chile's 29 congressional districts, Chile's Marxist President suffered an embarrassing setback.
The congressional by-election involved Allende's home province of Valparaiso in central Chile. In last fall's presidential balloting, Allende...