Republican Turnout Was Disappointing, But Democratic Turnout Was Truly Dismal
Between 2008 and 2016, the share of eligible voters voting for the Republican nominee fell 6.7%, while the share of eligible voters voting for the Democratic nominee fell 17.7%. These figures are derived from an extended analysis of the number of eligible voters, as opposed to the total population or number of likely voters in both 2008 and 2016. That analysis also casts light on the importance of policies like felony disenfranchisement in some key battleground states that worked to the detriment of Democrats.
These numbers show a stark divide between the parties in a year where the public had an unfavorable opinion of both major party nominees throughout the election. But, it overstates slack in Republican turnout because its main demographics are shrinking in the share of eligible voters over the last eight year, while it understates the degree to which Democrat voter turnout collapsed in 2016, because the main Democratic party demographics have been growing since 2008.
Republican Voters Are More Reliable And Loyal To Their Party Than Democratic Leaning Voters
Donald Trump won at a time when the an economic situation that was more or less neutral between the two political parties based upon historical experience, although it may have slightly favored Republicans. The overwhelming rejection of Trump by the mainstream media, by many corporate elites, and even by significant elite figures in the Republican party.
Donald Trump won, despite being an unprecedentedly bad major party nominee for the Presidency, because Republican voters have had very consistent and solid turnout over the years despite a lack of a good field organization in 2016, and because Republican voters collectively and overwhelmingly decided to put their partisan allegiances above the failings of their particular candidate this year.
In contrast, Democratic leaning voters are notoriously fickle and failed to turn out to vote for Hillary Clinton at previous levels, despite a par for the course field organization and more professional campaign management, because a large share of Democratic leaning voters were uninspired by her candidacy and do not have such unwaivering partisan loyalty.
The Electoral College Is Rigged In Favor Of Republicans
Trump's win also highlights the fact that under the current electoral college system, a Republican can lose to a Democrat in the popular vote by a non-trivial margin (about a million votes in 2016) and yet still win the electoral college. Basically, the current system is rigged in a way that requires the Democrat to win 52%-54% of the popular vote under reasonably normal circumstances, to win the Presidency.
Trump's Run Had No Coat Tails, But Clinton's Poor Performance Hurt Down Ticket Democrats
While Donald Trump had few coat tails in down ticket voting which saw Republicans lose a modest number of seats in both the House and the Senate, the poor Democratic turnout caused by Clinton's uninspiring campaign also denied Democrats the Congressional gains that they would have secured with a strong candidate (which looked like they might materialized even on the eve of the election).
Bad Polling Led To Bad Tactical Choices
It is also, of course, notable, the polling nationwide conducted by a great many firms, almost across the board, greatly underestimated the amount of support that Donald Trump had with likely voters for reasons that are still to be determined. This reduced the urgency of Democratic field operations and Democratic leaners felt need to vote, in states that turned out to be close but were not expected to be so close, and also led Clinton to misallocate campaign resources in the manner that she would have if she had had access to more accurate polling information.
Further Research
It will be worth the effort to look at turnout data more closely on a state by state basis in battleground states to discover the most important trends driving low Democratic turnout in 2016.