President Biden will nominate former senator Jeff Flake (R-Ariz.) to serve as ambassador to Turkey, the White House announced Tuesday.

Flake, who served in Congress for 18 years, became a vocal critic of then-President Donald Trump and ultimately endorsed Biden ahead of the 2020 election.

Flake will become the second Arizona Republican to be nominated for an ambassadorship after Cindy McCain, the widow of John McCain, the longtime Republican senator. Cindy McCain was nominated for a United Nations posting in Rome, serving at the agencies for food and agriculture.

The president will also nominate Kent Doyle Logsdon, a career Foreign Service member, to serve as ambassador to Moldova.

The support of Flake and McCain helped Biden win Arizona, a state that the Republican nominee had captured in every previous election dating to 2000.

“With this nomination, the Biden administration reaffirms the best tradition of American foreign policy and diplomacy: the credo that partisan politics should stop at the water’s edge. U.S. foreign policy can and should be bipartisan. That is my belief as well, and my commitment,” Flake said in a statement.

While Turkey remains a strong NATO ally, its relationship with the United States has been fraught, posing a challenge for Flake.

Biden has criticized Turkish President Recep Tayyip Erdogan for arrests of journalists, political opponents and academics, calling him an “autocrat.” In May, Erdogan accused Biden of having “bloody hands” for selling arms to Israel, comments that the State Department called antisemitic.

The two leaders met last month during the NATO summit in Brussels, with both men describing the session as positive though they made no breakthroughs on the more difficult geopolitical issues such as Turkey’s purchase of missiles from Russia and the wars in Syria and Libya.

Turkey is home to Incirlik Air Base, which is used by the U.S. Air Force and is considered key to military operations in the Middle East.

The Biden administration is striving to nominate a diverse group of ambassadors, an effort that has contributed in part to the slow rollout of nominees. Biden has also vowed to nominate a lower percentage of political ambassadors compared with previous administrations.