Alex Vindman, who became a key player along with his twin brother in Donald Trump’s first impeachment, announced on Tuesday that he is running for the US Senate as a Democrat in Florida.

Vindman, an army veteran, was serving on the national security council in 2019 during Trump’s first presidency. That year, Trump pressured Ukrainian leader Volodymyr Zelenskyy to investigate Joe Biden.

Vindman and his brother, Eugene, a lawyer on the national security council, reported their concerns and sparked investigations – before Trump would lose the 2020 presidential election to Biden.

Eugene Vindman now serves as a congressman from Virginia. If Alex Vindman clinches the Democratic nomination, he will challenge Republican US senator Ashley Moody, a former state attorney general who was appointed to fill the seat vacated by Marco Rubio as he became secretary of state for Trump’s second presidency.

The winner of November’s special election will finish the last two years of Rubio’s term.

Vindman described Trump as a “wannabe tyrant” and federal immigration agents as “thug militias” in his announcement video, which features the recent killing of US citizens Renee Nicole Good and Alex Pretti during the federal deportation campaign in Minnesota.

Vindman was forced out of the national security council and later retired from the US army after testifying against Trump during impeachment hearings. He said: “This president unleashed a reign of terror and retribution, not just against me and my family but against all of us.”

He urged voters to “stand with me now to put a check on Donald Trump and the corrupt politicians who think your tax dollars are their personal piggybank”.

Vindman becomes the most prominent Democrat in the Senate contest in Florida as the party tries to reclaim majorities in Congress in the fall midterm elections.

Their task in Florida will not be easy. The onetime swing state, which is Trump’s legal residence, has swung decidedly red in recent years. A Democrat has not won a Senate seat there since 2012.

Still, Democrats are hopeful that Vindman’s fundraising prowess and the national political environment – including the backlash against Trump’s immigration crackdown and his lack of focus on the economy – gives them a chance.

Trump denied any wrongdoing when he was impeached, and he was acquitted by the Senate. He later was impeached over the deadly 6 January 2021 US Capitol attack carried out by his supporters and again was acquitted.