(CNN) The early days of the 2020 presidential primary have shown the Democratic Party is in flux and having a robust debate about what its future will look like. And while that debate is centered on progressive policies like "Medicare-for-all," the Green New Deal and how much to tax the rich, it's being fueled by shifting demographics within the party.

From 2013 through 2018, an average of 46% of Democrats identified as "liberal," compared with 35% of respondents who said they were "moderate" and 17% who called themselves "conservative," according to Gallup.

That's a stark jump from the previous six years: From 2007 through 2012, those who identified as "liberal" or "moderate" were basically the same -- 39% and 38%, respectively.

The research comes amid a crisis of self in the Democratic Party -- whether the winning strategy in a growing field of candidates is to nominate a presidential candidate who will take a moderate position on hot-button issues or to nominate one who is likely to take a more liberal stance.

The change is largely driven by the increasingly liberal leanings of whites and college graduates within the party.

In the last six years, more than half of white Democrats, 54%, identified themselves as "liberal." That's a 20-point jump from the average in 2001-2006. By comparison, the percentage of Hispanic Democrats and black Democrats identifying as liberal grew 9 points and 8 points, respectively, in that same time frame.

College-educated Democrats have long been more likely to identify as liberal than those without college degrees, and the percentage of Democrats who reported having a college education grew 17 points from 2001-2006 to 2013-2018.

Those educated groups have grown increasingly liberal over lime, with the percentage of Democrats with college degrees who identify as liberal jumping 16 points from 2001-2006 to 2013-2018. The percentage of Democrats with post-graduate degrees identifying as liberal also jumped 13 points in that time frame, outpacing the growth among people with some college education (12 points) and no college education (10 points).

That shift toward liberalism can, again, be chalked up to a change in white Democrats -- this time in the growth of educational attainment. Gallup's research shows an average of 42% of white Democrats reported having college degrees in 2013-2018 -- a 13-point jump from 2001-2006. In that same period, the percentages of black Democrats and Hispanic Democrats with college degrees grew 3 points and 1 point, respectively.

According to Gallup, the shift toward liberalism within the party is being set by leaders in Washington and politics at large -- as leaders present more leftist views on policy, the party follows.

While white Democrats are fueling a shift toward the left in the party, they are making up a shrinking share of its makeup.

According to the research, the percentage of nonwhite Democrats has gone up to an average of 43% in 2013-2018 from an average of 31% in 2001-2006. White people now make up 56% of the party, a 12-point drop from 2001-2006.

Those nonwhite Democrats are also the least likely ones to identify as liberal. According to Gallup's research, 17% of liberal Democrats are black, 13% of liberal Democrats are Hispanic and 65% of liberal Democrats are white. In comparison, conservative Democrats are 35% black, 22% Hispanic and 40% white.

The number of Democrats who identified as having "no religion" has also doubled (20% in 2013-2018) since 2001-2006. The country as a whole has seen more people picking "no religion" when asked about their religious identity, but the pace is more pronounced among Democrats, according to Gallup.

There are places where the party still agrees almost completely, namely on stricter gun laws and labor unions, but breaks are seen on the issues of abortion and health care.

Health care has already been a main focus in the 2020 campaign. Sen. Kamala Harris, of California, made waves with her support for Medicare-for-all in a CNN town hall, escalating an intraparty debate on the right way for the party to approach health care. Earlier this week, Sen. Amy Klobuchar, of Minnesota, disagreed with Harris, arguing for a more pragmatic approach.

According to Gallup, an average of three-quarters of liberal Democrats in the last six years preferred a government-run health care system, while about half of moderate Democrats and 42% of conservative Democrats agreed.

The research is based on combined data from Gallup's multiday cross-sectional national telephone polls conducted by cellphone and landline each year from 2001 through 2018. The results are summarized in six-year periods and include interviews with 73,303 Democrats for 2001-2006, 48,195 Democrats for 2007-2012 and 32,830 Democrats for 2013-2018.

Results based on these samples have margins of sampling error of less than ±1 percentage point at a 95% confidence level.