Alex Vindman, who became a key player along with his twin brother in President Donald Trump’s first impeachment, announced on Tuesday that he is running for the U.S. Senate as a Democrat in Florida. Vindman, an Army veteran, was serving on the National Security Council in 2019 when the Republican president pressured Ukrainian President Volodymyr Zelenskyy to investigate Joe Biden, then a Democratic candidate. He and his brother, Eugene, a lawyer on the National Security Council, reported their concerns and sparked investigations. Eugene Vindman now serves as a congressman from Virginia. If Alex Vindman clinches the Democratic nomination, he’ll challenge...