2017 - 17 Intelligence Agencies
The Hillary Campaign Talking Point was that "17 intelligence agencies" agreed that Russians had hacked the election. The NYT printed it and CNN repeated it for years. James Clapper admitted in front of congress that was bullshit and that he only had 3 (or 4) agencies under his purview, and that 2 of them had disagreed until pressured. CNN repeated it long after it was debunked, and never retracted or corrected the record, which is why their viewers still think it's true. NYT and others at least offered corrected versions later.