As Democrats try to hold the Senate through defending red states, a look at the rise and fall of split Senate outcomes in presidential years.KEY POINTS FROM THIS ARTICLE— This is the second part of our history of presidential-Senate split-ticket results, from World War II to now. This part covers the mid-1980s to present, a timeframe that started with many instances of split results and ended with hardly any at all.— In 1984 and 1988, amidst large GOP victories at the presidential level, more than a dozen Republican-won states sent Democrats to the Senate both years.— The 1990s, when Democrats were successful at the presidential level, split-ticket voting tended to benefit Republicans in the Senate, making the decade an exception in the postwar era.— In the 2000s, Democrats were back to benefitting from the split-ticket dynamic, first under a Republican president, George W. Bush, then with a Democrat, Barack Obama.— Montana, a state which Senate Democrats are defending this year in a Toss-up race, is the state that has split its ticket most often in the postwar era. And almost every state has split its ticket at least once during that time.