Complex sentence: Whether by informal deal or simply reassurances already in line with Hayes's announced plans, talks with Southern Democrats satisfied the worries of many and so prevented a Congressional filibuster that had threatened to extend resolution of the election dispute beyond Inauguration Day 1877.
Split into simpler sentences: Whether by informal deal or simply reassurances already in line with Hayes's announced plans, talks with Southern Democrats satisfied the worries of many. This prevented a Congressional filibuster that had threatened to extend resolution of the election dispute beyond Inauguration Day 1877.