Mr. Trump can be credited with prompting, however inadvertently, the most profound period of press self-assessment in decades — and it comes at a period of unusual financial peril for the mainstream media. All around are sad affirmations of the diminishing credibility of the press, disheartening reminders that at least a third of the country, and perhaps more, regards our work as meaningless, biased or untruthful. In newsrooms, as at newsstands across the country, difficult but vital questions about the methods and motives of the press are being raised, forcing newsmongers and consumers of news to question long-held assumptions.