Robert Merry sees the election as a referendum on Obama’s second term:
In this view, we have been looking in the wrong places as we assess the campaign. Instead of focusing on Trump and Democrat Hillary Clinton, we should be looking at the presidential performance of Barack Obama—and not his overall tenure but specifically his second-term record.
Merry makes an interesting case that for why the incumbent party candidate is at a disadvantage this year, and I recommend reading the entire article to see why he thinks so. I agree that Obama and his record matter to the outcome of the election, but that leads me to think that Trump is the one at a disadvantage. Alan Abramowitz reviewed the evidence from postwar open presidential elections and found that the incumbent party candidate tends to win the popular vote when the president’s approval rating is over 50%:
The fate of the incumbent party’s candidate is strongly influenced by the popularity of the outgoing president. In fact, the incumbent president’s approval rating explains over half of the variance in the vote share of his party’s nominee. All three candidates seeking to succeed presidents with approval ratings below 50% were defeated, and the two seeking to succeed presidents with approval ratings below 40% were decisively defeated. In contrast, two of the three candidates seeking to succeed presidents with approval ratings above 50% won the popular vote, although one of those candidates, Al Gore in 2000, ended up losing the electoral vote.
Obama’s approval rating has been averaging over 50% for many months, and it has been mostly climbing since the spring. That indicates that Clinton is the slight favorite to win. It’s possible that something could happen to sour the public on Obama in the final weeks of the election, and it’s certainly possible that Clinton could fritter away this advantage, but if the election turns on the public’s approval of how Obama has done his job we should expect the Democratic candidate to win the popular vote in November. There is a chance that Trump could win in the Electoral College in spite of this, but that is a very unlikely outcome.