Former Arizona sheriff Joe Arpaio is in a statistical tie with Rep. Martha McSally (R-Ariz.) in the Republican Senate primary in Arizona, according to a new poll.

The ABC15/OHPI poll shows 85-year-old Arpaio, who on Tuesday announced his plans to run for the Senate seat, has 29 percent support in the race.

McSally, 51, who is also expected to jump into the race soon but has not made a formal announcement, has 31 percent support, according to the poll.

Former state Sen. Kelli Ward, 48, has 25 percent support in the poll.

The poll was conducted Tuesday among 504 likely Republican voters. Its margin of error is 4.36 percentage points.

Arpaio gained popularity among immigration hard-liners during his time as Maricopa County sheriff, proudly calling himself "America's toughest sheriff" and touting a strict approach to border security.

President Trump pardoned Arpaio last year after he was convicted of ignoring a court order related to racial profiling in his office.

McSally, who is expected to jump into the race soon, could stand to benefit from Ward and Arpaio's similar constituencies if the candidates split each other's votes.