Hey Kicky, sorry about that. Glad that Cyclo already jumped in to explain. To summarise:
- Each line (except the dotted one) represents the results of one daily tracking poll.
- The value of each line is the percentage Barack Obama is getting minus
the percentage John McCain is getting.
- That's also the numbers on the left, then. Above 0 (and the thick black line) means an Obama lead; under it means a McCain lead.
Example: today, the Research 2000/Kos poll (the lightest blue line) has Obama at 48%, and McCain at 44%. 48 minus 44 = a 4 point lead, so the lightest blue line in the chart is at +4 today.
Diageo/Hotline today has a 3-point Obama lead, Gallup a 2-point Obama lead, and Rasmussen a 1-point McCain lead, so the other blue lines clock in at +3, +2 and -1.
The dotted blue line, meanwhile, is a trendline, derived from the daily averages of these daily tracking polls.