The sample covers 1,002 adults and covers the dates of September 19-October 2. Repondents were divided into “lean-Republican” voters and “registered voters.” From the Post’s story:

After a quick rise in the race for the Republican presidential nomination, Texas Gov. Rick Perry has experienced an almost equally dramatic decline, losing about half of his support over the past month, according to a new Washington Post-ABC News poll. Perry’s slide, which comes after several uneven performances in candidate debates, has allowed former Massachusetts governor Mitt Romney to resurface atop the GOP field. But the most direct beneficiary of the disenchantment with Perry is businessman Herman Cain, who is now tied for second place.

The poll found that Romney had regained the lead: Romney 25% Perry 16% Cain 16% Christie (not an announced candidate) 10%