Endorsements in the Democratic presidential primary race are seemingly following a pattern: Every major union or progressive group that let its members vote has endorsed Vermont Sen. Bernie Sanders, while major organizations that had their leaders decide have typically opted for former Secretary of State Hillary Clinton, reported the Intercept Friday.

The news site noted that several of the endorsements for Clinton were accompanied by critiques from some members who felt left out of the process. "It’s perhaps the clearest example yet of Clinton’s powerful appeal to the Democratic Party’s elite, even as support for Sanders explodes among the rank and file," the Intercept wrote.

Clinton received a major endorsement from the Human Rights Campaign this week, which the Intercept noted was not made by the group's members but by a 32-member board of executives. "It’s understandable and consistent with the establishment organizations voting for the establishment candidate, but it’s an endorsement that cannot possibly be based on the facts and the record," Sanders spokesman Michael Briggs said.

Groups like the American Federation of State, County and Municipal Employees, the National Education Association and the American Federation of Teachers all endorsed Clinton with a top-down process that some members took issue with, according to the Intercept.

Data-focused website FiveThirtyEight has tracked endorsements from politicians, not groups, during the primaries, saying they "have been among the best predictors of which candidates will succeed and which will fail." Clinton has seemingly proven to be the party establishment choice, earning 458 points — FiveThirtyEight's scale awards 10 points for governors, 5 points for U.S. senators and 1 point for U.S. representatives -- to Sanders' 2 points.

Front-runner Clinton's lead has slipped significantly, leaving her campaign nervous. The latest polls ahead of the Feb. 1 Iowa caucuses show her leading Sanders in the state by just 2 percentage points, which falls well within the margin of error.