WASHINGTON, Aug. 20 (Xinhua) -- A total of 74 former Republican national security officials released a letter Thursday, saying they will elect Democrat Joe Biden as the next U.S. president in the November election.

Shortly before Biden, a former U.S. vice president, was scheduled to deliver a speech formally accepting the Democratic nomination for president, the letter said the signatories "are firmly convinced that it is in the best interest of our nation that Vice President Joe Biden be elected as the next President of the United States, and we will vote for him."

The former officials, an expanded cohort compared to the 50 of them who also opposed electing Trump in the 2016 election cycle, said in the letter that they "are profoundly concerned about our nation's security and standing in the world under the leadership of Donald Trump. The President as demonstrated that he is dangerously unfit to serve another term."

In 2016, these people said "none of us will vote for Donald Trump," adding, however, that many Americans "have doubts about (then Democratic presidential nominee) Hillary Clinton, as do many of us."

Trump, for his part, has been campaigning in key battleground states throughout the week. On Thursday, he stopped near Biden's birthplace of Scranton, Pennsylvania, for some counterprogramming hours before Biden's acceptance speech.