Pope Francis' popularity in the United States has taken a hit, especially among conservatives.

About six in 10 (59 percent) of U.S. adults now have a favorable rating of the pontiff, a 17 percent drop since February 2014 when it was 76 percent, according to a new Gallup poll.

The largest drop in approval was found among conservatives, whose favorability rating of Francis fell a whopping 27 percentage points — 72 percent in 2014 to 45 percent in 2015. That drop could be explained by the pope's recent remarks in which he criticized capitalism and said people need to worry more about how human activity affects the environment.

But his approval among Catholics has also dropped 18 percent over the last year and a half, from 89 percent in 2014 to 71 percent in 2015. Among Protestants and other Christians, his approval fell 21 points over that same period, to 52 percent in 2015.

His image among liberals and moderates has also taken a hit. Sixty-eight percent of liberals and 71 percent of moderates view Francis favorably in 2015, down 14 and 8 points from 2014, respectively.

Since 2014, more U.S. adults say they have an unfavorable opinion of Francis, from 9 percent in 2014 to 16 percent in 2015. A quarter of Americans have also never heard of him or have no opinion of him, an increase from 16 percent in 2014.

Francis was elected leader of the Roman Catholic Church in March 2013. Though his numbers are better than those of his immediate predecessor Pope Benedict XVI, they are not quite as good as Pope John Paul II, who at one point had a favorability rating of 86 percent in 1998.

Francis is slated to make his first visit to the U.S. in September, traveling to Washington, D.C., New York and Philadelphia.

The telephone-based poll of roughly 1,000 U.S. adults was conducted July 8-12 with a margin of error of plus or minus 4 percentage points.