Donald Trump is sinking — and fast.

His poll numbers have plunged at both the national and battleground-state levels as a series of past misogynistic remarks and allegations of sexual misconduct have emerged over the last two weeks. The brash exuberance that accompanied his September rebound has morphed into bitter anger over what the GOP nominee perceives as a media conspiracy to rob him of victory in the upcoming election, and to hand the White House to Democrat Hillary Clinton.

"The election is absolutely being rigged by the dishonest and distorted media pushing Crooked Hillary," Trump tweeted on Sunday. Trump also alleged that "many polling places" had been corrupted, even though most states have not yet opened their polling stations. Most of the states where early voting has begun use the mail rather than polling stations.

Trump and his campaign have not produced any evidence to back up allegations of America's voting system being rigged against him.

But that doesn't mean Trump's accusations of media bias are baseless. Indeed, these charges are on very solid footing.

The media bias about which Republicans have long complained has become undeniable reality in the 2016 campaign. Now, it's not hard to see why the national media is biased against conservatives. While there are plenty of conservatives working at national newspapers and political magazines in New York and Washington, the bulk of the journalists that comprise what most Americans think of as the "mainstream" media lean left. It doesn't take some cabal of liberal journalists hatching anti-Republican plots in the middle of the night to achieve the media's broad anti-Republican bias. It just takes an industry that tends to employ more liberals than conservatives. For example, journalists have given nearly $400,000 to Hillary Clinton's campaign. And Trump's?

The watchdog Center for Public Integrity on Monday said that journalists favored Clinton 27-1 over Trump, who got a tiny $14,000.

Some 430 in the media business donated to Clinton compared to 50 to Trump. [Washington Examiner]

You can see bias in the actual coverage, too. A study from Harvard's Shorenstein Center of the four weeks encompassing and surrounding the two major-party political conventions makes this obvious. Trump's news coverage during this period was 75 percent negative; the friendliest week Trump got from the media was the week of the convention itself — when it was "only" 55 percent negative

Contrast that with the treatment Hillary Clinton received in the same period, which overall was 44 percent positive. Where no news outlet in the Shorenstein study managed to get to 40 percent positive coverage of Trump, all but one (Washington Times) had 40 percent or more positive coverage of Clinton. Four of the 11 media outlets offered better than 50 percent positive coverage to Clinton. While coverage of Trump's qualifications only generated 22 percent positive coverage, 69 percent of the coverage of Clinton's leadership qualities was positive.

You might argue that Trump's convention was objectively more divisive, scattered, and negative than Clinton's, and the coverage simply reflected that. But that surely can't account for all of this disparity. Some of it, undoubtedly, is due to journalists' (often subtle and unconscious) bias.

But Trump didn't always suffer from media bias. In the GOP primaries, the media was arguably biased in his favor.

"From the time he announced his candidacy until the start of the conventions," Shorenstein study author Thomas Patterson writes, "Trump had not experienced anywhere near the press criticism directed at him during the final two weeks of the convention period." The media shift becomes all the more remarkable when considering an earlier study by Patterson about media coverage in 2015. Not only did the media obsess over Trump, providing him with an estimated $55 million in earned media, but the coverage provided by the same outlets was considerably more benign. "Across all the outlets," Patterson notes, "Trump's coverage was roughly two-to-one favorable."

Republicans have long contended with media bias. That was one of Trump's supposed selling points — that his celebrity would outmatch any bias in the media, and that his own media savvy would make him unbeatable. Republicans who prized victory over policy or character backed Trump because he would hold nothing back, taking the fight to the Clintons and using his mastery of media manipulation to benefit the GOP. Skeptics pointed out that Trump's long and controversial history in business and the media made him particularly vulnerable to late-season attacks based on opposition research — and that primary media coverage patterns would not hold up in the general-election season.

Clearly, the skeptics got it right.

And though the media is biased against Republicans, the truth is that most of the damage done to Trump in the last few months has been either inflicted or seriously exacerbated by himself — and all of that belies the argument that Trump's supposed skills at media mastery was all Republicans really needed to win the White House.