Complex sentence: Foreseeing a long and costly political battle, many labor unions chose to campaign for employer-sponsored coverage, which they saw as a less desirable but more achievable goal, and as coverage expanded the national insurance system lost political momentum and ultimately failed to pass.
Split into simpler sentences: Foreseeing a long and costly political battle, many labor unions chose to campaign for employer-sponsored coverage, which they saw as a less desirable but more achievable goal. The national insurance system lost political momentum and ultimately failed to pass.