Their concerns were prompted by a string of stories by The Washington Free Beacon, a conservative website that extensively reviewed archival material at the Clinton presidential library in Little Rock, Ark., and came up with an audio tape of Mrs. Clinton discussing a rape case she had worked on as a defense lawyer in the 1980s.
The tape was a reminder that, with so much scrutiny applied by the news media and Mrs. Clinton’s opponents in her public life, it’s a challenge for rivals to come up with new material, and to make any fresh information stick. That was a frequent problem for President Obama’s campaign when he ran against Mrs. Clinton in the primaries in 2008, when both were senators.

More recently, Republicans and reporters have turned their sights to the Bill, Hillary & Chelsea Clinton Foundation for accepting donations from foreign countries after Mrs. Clinton left the State Department. The scrutiny has focused on which entities donated to the foundation, and whether there was any overlap with Mrs. Clinton’s diplomatic work.