The poll was comissioned and paid for by Tonko's campaign. It says so on the top of each page. It will tend to be slanted in his favor.
Of course, he has greater name recognition due to his experience in the legislature, and so he has greater positive image. But, with high name recognition, 56% favorability rating doesn't seem very strong.
Steck's and Brook's campaigns have a long way to go in name recognition. Steck has been hurt by media opposition, by underreporting on his campaign early, and minimizing his Albany County endorsement by playing into Jenning's grandstanding.
I think Brooks is being hurt by Clinton's loss of the Democraic nomination, and Jenning's slide in influence. She may still pull out a win, since Tonko and Steck will split the more liberal and progressive vote. I think Obama's campaign helps Steck more than Tonko, since Steck is more of an underdog grassroots campaigner, and a change candidate who represents a new direction not only for the country, but within the Democratic Party.
Skyrocketing gas prices could influence the campaign, by making alternative energy an issue. Tonko could have some real negatives here, since his experience is in energy policy. His role in the deregulation of the energy corporations, and his support for renewed nuclear energy development, could hurt him, if his opponents can get the media to report on his positions.
The outcome will depend a lot on who else can stay in the race. Lester Freeman, especially, could pull some Albany and African American votes from Steck and Tonko, and help Brooks. Shahinfar will pull some progressive votes if he stays in, also helping Brooks.
If Brooks wins the Democratic Primary, Tonko can run on the Working Families Party line. I thnk he would have a very good chance of winning a three way race. It would probably be a high priority for the WFP, and they have the organization to pull it off.