Felony convictions and guilty pleas by two close associates had little initial effect on President Donald Trump's political standing, and Republicans remain in an uphill fight to keep control of Congress.

Those are the findings of new NBC News/Wall Street Journal polls, conducted both before and after bombshell legal developments in the federal investigations of Trump and his campaign. In one survey mostly conducted before those developments, 46 percent of American voters approved of Trump's job performance; in an additional survey conducted entirely afterward, 44 percent approved, a decline that fell within the margin of error.

At the same time, Democrats held an 8 percentage point national lead over Republicans in the race for the House. Their 50 percent to 42 percent advantage puts Trump's political adversaries in a promising position to gain the 23 seats they need for a House majority approaching the final two months of the mid-term election campaign.

The first survey of 900 registered voters, conducted by telephone August 18-22, carries a margin for error of 3.27 percentage points. The second survey of 600 registered voters, conducted by telephone Aug. 22-25, carries a margin for error of 4 percentage points.

A federal jury outside Washington convicted Trump's former 2016 campaign chairman Paul Manafort of eight felony fraud counts on Tuesday Aug. 21. That same day, Trump's former personal lawyer Michael Cohen plead guilty in New York to eight felony counts, including two related to the payment of hush money to women who alleged they had affairs with Trump. Trump has previously denied having affairs with either woman.