"If the disgusting and corrupt media covered me honestly and didn't put false meaning into the words I say, I would be beating Hillary by 20%," Trump said on Twitter this morning.
He added to the comments throughout the day on social media.
"It is not "freedom of the press" when newspapers and others are allowed to say and write whatever they want even if it is completely false!" he tweeted Sunday afternoon.
Trump's barrage comes after a spate of unfavorable polls over the past week.
The most recent ABC News/Washington Post poll showed that Hillary Clinton has advanced among women and consolidated support within her party since her nominating convention, while a difficult few weeks left Donald Trump still struggling on basic ratings, from his temperament to his qualifications for office. She led him by 8 points in the poll published Aug. 7.
Another poll this past week by NBC News/Wall Street Journal/Marist showed Clinton leading Trump by 9 points in the swing state of Pennsylvania and gaining in other battleground states.
Compounding the downward trajectory of Trump's polling data is apparent pressure from a portion of the conservative electorate that has failed to coalesce around his candidacy.
New independent candidate for president Evan McMullin, a conservative, said Sunday on ABC's "This Week" that his entrance into the race won't affect Donald Trump's chances because "it's so likely that [he] will lose."
In another tweet, Trump referred to the large size of his rallies and the passion of his supporters, claiming that these details have been ignored by reporters.
"My rallies are not covered properly by the media," he said in Connecticut. "They never discuss the real message and never show crowd size or enthusiasm."
To emphasize the statement he made Saturday at the rally in Fairfield, Connecticut, about the "crooked media", the 70-year-old real estate tycoon waved his finger in a horizontal line toward where the press was stationed.
In May, he called ABC News' Tom Llamas a "sleaze."