Complex sentence: The reduction in the number of two-member constituencies ended cross-party cooperation: before the Act, in many counties and boroughs the two main parties had agreed to nominate one candidate each, and no election was held.
Split into simpler sentences: The reduction in the number of two-member constituencies ended cross-party co-operation. Prior to the Act, in many counties and boroughs the two main parties had agreed to nominate one candidate each, and no poll was held.