Can the atmosphere below thunderclouds act as a giant spark chamber for the detection of ultrahigh-energy shower cores or relativistic monopoles? The return stroke of ordinary lightning is crooked because the stepped leader is crooked and changes direction at most steps. In multiple strokes the subsequent strokes are preceded by a leader following the ionization channel of the previous return stroke. The cause of leaders occasionally leaving old stroke channels is found to be atomic and molecular negative ions inside and outside old stroke channels, respectively. From this it is shown that the ionization in shower cores and possibly that in monopole paths would be capable of carrying a lightning leader which would then be straight and result in a straight return stroke. An important question is: Would the ionization from a shower core or relativistic monopole initiate a lightning leader? It is shown that radio emission plus shower counter data may be able to answer this. Artificial initiation of lightning shows that even thunderclouds without spontaneous lightning maintain large potential gradients over large areas for significant periods of time. Straight lightning may lack the normal preleader radio emission of spontaneous lightning. Thundercloud conditions for straight lightning may be more favorable over ocean than land areas.