WASHINGTON (Reuters) - Republican U.S. Representative Martha McSally of Arizona said on Friday she would run for the Senate seat being vacated by Jeff Flake, joining a contentious primary contest.


Republican leaders had been pushing for McSally, a former Air Force combat pilot seen as a more moderate candidate, to enter a primary race that already includes former Arizona Sheriff Joe Arpaio, an ally of U.S. President Donald Trump, and Kelli Ward, a former doctor and Arizona state senator who has already made a failed bid for the U.S. Senate as a conservative.


"After taking on terrorists in combat, the liberals in the Senate won't scare me one bit," McSally, 51, said in a YouTube video.


McSally, who has been a U.S. representative since 2015, is scheduled to hold events in Tucson, Phoenix and Prescott, Arizona, on Friday. The Arizona Democratic Party announced on Thursday that it would protest the events.


"Arizonans know Congresswoman McSally is just another typical politician who says one thing and does another - all in hope of winning elections and attracting votes," the party said in a release.


McSally filed a lawsuit against the U.S. Department of Defense in 2001, when she challenged the military policy requiring female service members to wear the traditional Gulf Arab abaya gown when off base in Saudi Arabia. The Senate overturned the policy the following year.

Arizona holds its primary in August. The winner of the Democratic primary is likely to be Kyrsten Sinema, the first openly bisexual person elected to Congress.

(Reporting by Blake Brittain; Editing by Lisa Von Ahn)