Why Barack Obama’s popularity matters to Hillary Clinton
When George H.W. Bush ran for the presidency in 1988, he was running as the second-in-command to a still-popular Ronald Reagan. He beat Democrat Michael Dukakis handily. When his son ran in 2000, he was running against the second-in-command to a still-popular (more popular than Reagan, even) Bill Clinton. But he won.
Which raises the question: Next year, when a third Bush (or some other Republican) looks to succeed a two-term Barack Obama, how much does Obama's popularity matter?
The short answer, as the University of Virginia Center for Politics' Alan Ambramowitz wrote earlier this year, is that, historically, higher approval ratings for the outgoing president have correlated with a higher percentage of the popular vote for the member of his party looking to replace him. We'll note only now that George W. Bush won the presidency in 2000, but not the popular vote.
Ambramowitz figures that each 10 percentage points of approval for a president is worth about 1.8 percent of the popular vote for the candidate from his party. If Obama's at 50 percent approval, the eventual Democratic nominee, whoever she might be, might be expected to earn just more than half of the popular vote. If Obama's at 45 percent, Ambramowitz figures that Democrat is looking at just more than 49 percent of the vote.
http://www.washingtonpost.com/blogs/the-fix/wp/2015/05/17/why-barack-obamas-popularity-matters-to-hillary-clinton/