A conservative activist group tried to target Washington Post reporters, planting a source with a false allegation against Alabama Senate candidate Roy Moore. But instead of publishing the story of “Jaime Phillips,” who claimed Moore impregnated her at 15 and helped her get an abortion, the Post exposed the plot and foiled the operation to dupe its journalists. After the Post first published allegations on November 9 that Moore pursued relationships with teenagers and sexually assaulted a 14-year-old, the newspaper has been dogged by easily disprovable allegations that sources were biased, paid, or both. The conservative group Project Veritas and...