Maricopa County Sheriff Joe Arpaio's support waned after the recent revelations of his investigation into President Barack Obama's birth certificate, a poll released Thursday says.

The telephone poll of 600 likely voters concluded Arpaio's favorability rating dropped to 53 percent, and about 65 percent of respondents disapproved of the sheriff's investigating the president's birth certificate.

Arpaio continued to get high marks for being "tough on crime," with 76 percent of respondents approving of his work. But about 50 percent thought he did a poor job of keeping politics out of the Sheriff's Office and agency investigations.

The poll was commissioned by Citizens for a Better Arizona, whose leader, Randy Parraz, has been a consistent Arpaio critic, prompting Chad Willems, Arpaio's campaign consultant, to retort: "Of course he would put together a poll that would place the sheriff in a bad light."

The poll was conducted in early June. Arpaio's approval rating was more than 60 percent in 2008.