Stan Greenberg, whose work for the left at Democracy Corps is has inspired a new imitator, delivers the first salvo in what promises to be a spirited battle of pollsters.

In an open letter to Ed Gillespie, whose conservative policy group Resurgent Republic is modeled on Democracy Corps, Greenberg warns his colleague about the importance of unbiased research:

"For years, James Carville and I pushed Democrats and liberal groups to examine inherited positions in new times, but you are at risk of doing the opposite—urging Republicans to stay the course on key arguments with self-deluding results."

Gillespie, a former RNC chair and Bush advisor, launched Resurgent Republic with pollster Whit Ayres last week. Their inaugural poll suggested that while voters are fond of Obama, approval of his policies is more muted. In particular, the poll showed independents leaning closer to Republicans and 2-to-1 ratios of opposition against some Obama policies.

But Greenberg suggests these results come from a sample that is more conservative than the country's current make-up and from a text that uses loaded wording rather than the messaging employed by Democrats themselves.

"One thing Democracy Corps has tried to do is be very “conservative”—watching very closely to make sure all our choices in survey design are well grounded or tilted against the Democrats," Greenberg writes.

"While campaigns may succeed on 'gotcha,' you will not win a big argument if you do not respect the other side’s argument . . ."

Greenberg admits that when his group was launched 10 years ago, they made similar mistakes.

With both groups intending to make their survey results public while hoping to guide policy in different directions, expect more dialogue between the two.

"I look forward to the debate," Greenberg writes.

Read the full letter.