Duckworth is a Purple Heart recipient and a former Army helicopter pilot who lost both her legs in the Iraq War.
In February, the White House ousted Vindman from his post on the National Security Council. He had testified to Congress in November that he was disturbed by Trump’s call for Ukraine to investigate the president’s political rivals.
“Our military is supposed to be the ultimate meritocracy,” Duckworth said in a statement. “It is simply unprecedented and wrong for any Commander in Chief to meddle in routine military matters at all, whether or not he has a personal vendetta against a Soldier who did his patriotic duty and told the truth — a Soldier who has been recommended for promotion by his superiors because of his performance. . . . This goes far beyond any single military officer, it is about protecting a merit-based system from political corruption and unlawful retaliation.”
A spokesman for the Pentagon did not immediately respond to a request for comment.
Duckworth’s office described her move as “unprecedented in modern times” and said it was a response to “numerous efforts by Donald Trump to politicize the nation’s Armed Forces.” In recent weeks, the president has threatened to send active-duty troops to quell protests against police brutality and has used top military officials “as props for a photo op,” Duckworth’s office said.
The president posed for a photo with Gen. Mark A. Milley, chairman of the Joint Chiefs of Staff, and others near the White House in June after authorities forcibly removed peaceful protesters from the area — an appearance for which Milley was roundly criticized and later apologized.
Trump’s ouster of Vindman from the National Security Council in February was condemned as vindictive and an attempt to intimidate government officials who speak out against Trump. Asked at the time about Vindman’s future, the president said only that he was “not happy with him.”
“You think I’m supposed to be happy with him?” Trump said. “I’m not.”
Duckworth is the latest senator to seek to hold the president accountable by blocking promotions or the consideration of Trump nominees.
In June, Sen. Charles E. Grassley (R-Iowa), a longtime advocate for federal watchdogs, announced that he would block two of Trump’s nominees until the White House provided an explanation for the recent firings of intelligence community inspector general Michael Atkinson and State Department inspector general Steve Linick.
Grassley dropped his hold on the two nominees after receiving additional letters from the administration explaining the firing of Atkinson and Linick.
Shane Harris and Toluse Olorunnipa contributed to this report.
