Caspar Weinberger's indictment concerned a PRESIDENTIAL election. The former GHW Bush Secretary of Defense was indicted four days before the Bush-Clinton election. The indictment was thrown out in December.  By that point, Bill Clinton had already been elected.

You have to have probable cause to search e-mails. They have probable cause to search Anthony Weiner's e-mails related to Hillary Clinton. Until they get a warrant, it's safe to say at this time they don't have probable cause to search Trump's e-mails.