I must say, I've not considered this, but it does make sense. It seems there was more 'vote splitting' in this election than has been true for years. The writer makes the point that the decline of split voting has led to much more partisanship in the country.

http://thehill.com/homenews/state-wa...enate-majority

How ‘Never Trump’ voters saved Republicans’ Senate majority

BY REID WILSON - 08/02/17 06:00 AM EDT

Donald Trump became the first Republican presidential candidate in 28 years to win Pennsylvania and the first GOP candidate in 32 years to win Wisconsin’s electoral votes.

At the same time, Sens. Pat Toomey (R-Pa.) and Ron Johnson (R-Wis.) won reelection, in both cases overcoming polling deficits that showed them trailing their Democratic opponents.

On its face, it makes sense that if a Republican president won a state, a Republican senator would win reelection. But the underlying data shows Trump, Toomey and Johnson took very different paths to victory. Toomey and Johnson took advantage of an increasingly rare specimen of voter, the type willing to split their tickets between candidates of different parties running for different offices.

Republicans retained their narrow Senate majority because of the occasional voter who showed up to cast a ballot for Trump, but also because of “Never Trump” voters. This group leans Republican in any given election, but they could not bring themselves to cast a ballot for the party’s brash presidential nominee.

This is the fifteenth story in The Hill’s Changing America series, in which we examine the demographic and economic trends driving American politics today. Those trends have led to a starkly divided nation, one in which few voters are willing to split their ballots between candidates from different political parties.

The decline of the split-ticket voter helps explain the polarization dividing the nation’s politics today. It also helps explain why Trump has a lower approval rating among college-educated voters than among those without a college degree.

Political science research suggests those who pay the most attention to the news, those with higher levels of education — and, therefore, those more likely to have heard Trump’s most inflammatory comments — are much more likely to split their tickets. Those who are less likely to consume news, in both political parties, are more hardened partisans.

But split-ticket voters do exist, and both Democrats and Republicans have made concerted efforts to win them over.

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