President Trump needs every vote he got from white evangelicals in 2016 — and then some. Hoisting a Bible in the air may not be enough.

Unnerved by his slipping poll numbers and his failure to take command of the moral and public health crises straining the country, religious conservatives have expressed concern in recent weeks to the White House and the Trump campaign about the president’s political standing…

Robert P. Jones, chief executive of the Public Religion Research Institute, noted that since 2016, the share of the American population that is white and evangelical has declined by two percentage points, to 15 percent.

In March, nearly 80 percent of white evangelicals said they approved of the job Mr. Trump was doing, PRRI found. But by the end of May, with the country convulsed by racial discord, Mr. Trump’s favorability among white evangelicals had fallen 15 percentage points to 62 percent, according to a PRRI poll released Thursday. That is consistent with declines that other surveys have picked up recently. Among white Catholics, the same poll also found that his approval has fallen by 27 points since March.