Former President Barack Obama has had to leave behind his cushy post-White House retirement to help support the struggling campaign of Democratic nominee Vice President Kamala Harris, and he likely isn't particularly pleased about it.

Obama hit the campaign trail for Harris on Friday with an event in Arizona, where he masked his bitterness and anger with "withering mockery" of his successor, former President Donald Trump, the Republican nominee, according to The Washington Post.

That and other scheduled campaign appearances to bolster Harris down the final stretch have seemingly become necessary as she trails Trump in all of the major battleground states and has unusually low support among key demographic groups Democrats typically rely upon, such as black men.

Obama is back on the campaign trail for Harris

The Post reported that former President Obama spoke Friday at the University of Arizona in Tucson in support of VP Harris, though the majority of his remarks were reserved for scathing and belittling attacks against her opponent, former President Trump.

That has been a noticeable trend in Obama's "evolving role" with the Harris campaign, per the outlet, in that he initially quietly advised her from behind the scenes but has increasingly felt compelled to come out and launch direct assaults on the GOP nominee.

The trend will likely continue over the coming days, as the former Democratic president is scheduled to headline campaign events for Harris in swing states like Nevada on Saturday, Michigan and Wisconsin on Tuesday, and Georgia on Thursday.

It is at that Georgia event on Thursday, according to NBC News, that Obama and Harris will appear on stage together for the first time, and just a few days later on Saturday, Harris will likewise appear together for the first time with former first lady Michelle Obama at a rally in Michigan.

Harris desperately needs Obama's help

One possible reason why former President Obama has essentially been called out of retirement to help VP Harris close the deal is because she has shown herself to be incapable of doing it on her own.

Indeed, RealClearPolling's average of polls shows that Harris is only leading former President Trump by around a single point nationally, and he is beating her in all of the critical battleground states that typically decide modern elections, such as Arizona, Georgia, Michigan, North Carolina, Nevada, Pennsylvania, and Wisconsin.

Some polling also shows that Harris is well behind the norm with certain demographic groups that Democrats usually dominate, such as black men, according to the New York Post, a cohort the Trump campaign has been explicitly targeting with apparent success.

In fact, some polls suggest that the former Republican president could draw as much as 20-25% of the black male vote, which could potentially prove devastating to the Democratic nominee's presidential ambitions.

Scolding black men into voting for Harris may have backfired

That nightmarish scenario for Democrats was likely on former President Obama's mind last week when, at a Harris campaign event in Pennsylvania, he spoke on the sidelines directly to a group of young black men and seemed to patronizingly scold them and their brethren for not supporting VP Harris in sufficient numbers.

However, Newsweek reported that an online analysis of reactions to Obama's condescending remarks were nearly twice as negative as they were positive, and may actually have backfired and harmed more than helped Harris' chances with that key voting bloc.

It remains to be seen what sort of tone Obama will adopt for the rest of the election cycle -- a bitter ex-president viciously attacking his partisan opposition or a happy warrior excited about the prospects for the future -- and how he will be broadly received among the electorate and all of its various subgroups.