In tournament play, everything comes down to the size of your stack; it affects the way you play and it affects the way people play into you. Most players tend to challenge players with small stacks of chips rather than attacking the big stacks; there are two main reasons why players do this.
First, a player can very easily lose a large hand to a smaller stacked player but remain in the tournament. A small stack player can only commit a limited number of chips, if youre playing against a large stack, theres a danger your opponent will move all-in on you. People feel comfortable knowing that you will still be in the tournament if they play into a shorter stack. This behaiviour is understandable
Consider an online poker tournament that awards 5 seats. When there are six people left, everyone will be gunning for the person with the smallest stack. There is nothing to be gained from attacking someone with a large stack because that person will likely not be knocked out of the tournament. By attacking a large stack, you risk dwindling your stack and risking your own exit from the tournament. Thus, everyone will be attacking the smallest stack.
Since you probably do not want to be in the position of the smallest stack, the best method is to be selectively aggressive at stealing the blinds. As long as you keep your stack as high as the average player, people will not be gunning for you towards the end. You do not need to have the largest stack; you just need to have a medium-sized stack.
If you are in the unfortunate case of having the smallest stack, you will need to consider fighting back quickly. You do not want to get to the point where a double up will still leave you as the smallest stack. If you double up, you want someone else to be that small stack. No one wants to be the person that risks their chips to knock you out, so you should be aggressive in fighting back. If your stack is small but not microscopic, you will be amazed at how many blinds you still might be able to steal.