The largest single religious group in the Democratic Party is now the religiously unaffiliated, or “nones,” a new report by the Pew Research Center reveals.

In just seven years, the percentage of religiously unaffiliated among Democrats jumped a remarkable 47 percent, from 19 percent in 2007 to 28 percent in 2014.

The category of “religiously unaffiliated” comprises those who self-identify as atheists or agnostics as well as those who describe their religion as “nothing in particular.” According to the study, the religiously unaffiliated now account for 23 percent of the total U.S. adult population, up from 16 percent in 2007.

For the first time on record, fewer than two-thirds of Democrats and “Democratic-leaning” adults now identify with any branch of Christianity, the study found, down 11 percentage points since 2007. The decline in the number of Christians among Democrats was the single largest drop among the groups evaluated in the study.

In 2007, Catholics made up the largest single religious group in the Democratic Party, with 24 percent of the total. With a decrease to 21 percent, Catholics have now been superseded by the unaffiliated as the leading religious contingent among Democrats.

Nearly three-in-ten Democrats now say they have no religion whatsoever, up 9 points since Pew’s last Religious Landscape Study.

In contrast, Evangelicals make up by far the largest religious group among Republicans, with 38 percent of the total, a modest gain from the 37 percent in 2007. Catholics, on the other hand, historically affiliated with the Democratic Party, now are equally represented between the two parties, at 21% of both the Democratic and the Republican Party.

More than 80 percent of Republicans continue to identify themselves as Christians, spread predominantly among Evangelicals, Catholics and mainline Protestants.

Results come from the massive 2014 U.S. Religious Landscape Study, comprising a nationally representative telephone survey of 35,071 U.S. adults.

Follow Thomas D. Williams on Twitter @tdwilliamsrome