Complex sentence: This pledge backfired when, in August, Nixon injured his knee on a car door while campaigning in North Carolina; the knee became infected and Nixon had to cease campaigning for two weeks while the infected knee was injected with antibiotics.
Split into simpler sentences: This pledge backfired when, in August, Nixon injured his knee on a car door while campaigning in North Carolina. The knee became infected and Nixon had to cease campaigning for two weeks while the infected knee was injected with antibiotics.