Why, well assume for a minute that 30% of the voters will vote for Tom regardless and 30% will vote for someone besides Tom regardless.
So you basically need to get about 30% of the vote to have a shot.
First and foremost you need to get a fifth candidate in the race or get the number back down to three (since you would make the fourth candidate). With four and only four it is going to be too hard to beat Tom's built in incumbency with 5 you can get to a second round against a Tom.
So then to get enough to make it to a second round you need to appeal to a non-traditional base in Aurora.
Be very immigrant friendly (sanctuary city)
Be very immigrant unfriendly (police check your status) -- bigger risk with this one.
Try and appeal to 'new Aurora' that is the far east, west and south sides.
There are a few others as well.