WASHINGTON — House Republicans have spent months promising to use their majority to uncover an insidious bias against conservatives on the part of the federal government, vowing to produce a roster of brave whistleblowers who would come forward to provide damning evidence of abuses aimed at the right. But the first three witnesses to testify privately before the new Republican-led House committee investigating the “weaponization” of the federal government have offered little firsthand knowledge of any wrongdoing or violation of the law, according to Democrats on the panel who have listened to their accounts. Instead, the trio appears to be...