Former secretary of state Hillary Clinton waves to the crowd at the United Fresh Produce Association in Chicago, Illinois, June 10, 2014. (REUTERS/Jim Young)

As she embarks on a tour to promote her new book, former secretary of state Hillary Rodham Clinton's favorability rating is at its lowest point since 2008, a new Gallup poll released Wednesday shows.

Fifty-four percent of Americans say they hold a favorable opinion of Clinton, according to Gallup, down slightly from 59 percent in February.

Clinton's book "Hard Choices" was released Tuesday. She's been under the media spotlight as speculation swirls over the possibility she will run for president in 2016.

The last time Gallup showed Clinton's favorable rating as low as 54 percent was in August of 2008. During her tenure as the nation's chief diplomat, Clinton's favorable rating was in the 60s, as the following Gallup chart shows:


In the same poll, former president Bill Clinton's favorable rating is 64 percent.