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.

Perry also faces opposition to one of his signature immigration policies in Texas, the survey shows.

His rapidly changing fortunes underscore the fluidity of the Republican race and the lingering dissatisfaction with the candidates.

That has led some major donors and party leaders to urge New Jersey Gov. Chris Christie to declare his candidacy.