What effect is demonstrated by candidates who are leading in the polls tending to pick up support from voters who were undecided?

The above scenario refers to the BANDWAGON EFFECT.

The bandwagon effect happens when undecided voters cast their support to the candidate that has the most lead in the polls. They are thinking that since majority of the population is voting for him/her, then regardless of their personal sentiment, they will vote for the candidate that is most likely to win.

Hamlet's fourth soliloquy is probably his most famous one - "to be or not to be."it is rather different from his previous soliloquies because now he is contemplating something that didn't come up before - suicide. he is thinking whether it is worth it to fight to find his father's murderer when in the end all of them are going to die, so why not die sooner than later. he is contemplating if he should go on fighting or just kill himself and end it all, which is why this soliloquy in particular is rather depressing, hesitant, and gives a deeper insight into hamlet's madness.