Seven freshman Democrats in swing districts wrote in a Washington Post op-ed Monday that if allegations that President Trump tried to persuade Ukraine's president to investigate the son of 2020 candidate Joe Biden are proven true, it would "represent an impeachable offense." Several other Democrats came forward Monday to echo their calls.

This flagrant disregard for the law cannot stand."

— Washington Post op-ed by the freshman Democrats

Context: Trump confirmed Sunday that he discussed Biden and his son Hunter during a phone call with Ukrainian President Volodymyr Zelensky on July 25. Trump has flatly denied that he withheld aid in order to pressure Zelensky to investigate the allegations.

Ukraine's prosecutor general said in May that he has no evidence of wrongdoing by the former vice president or his son, following allegations by Trump's lawyer Rudy Giuliani of conflicts of interest related to Hunter's work with a Ukrainian energy company.

What they're saying: The Washington Post article was signed by Reps. Gil Cisneros (Calif.), Jason Crow (Col.), Chrissy Houlahan (Penn.), Elaine Luria (Va.), Mikie Sherrill (N.J.), Elissa Slotkin (Mich.) and Abigail Spanberger (Va.) who all represent competitive districts and all have national security backgrounds. The Democrats said they did not arrive at their conclusion on impeachment considerations lightly.

"[W]e call on our colleagues in Congress to consider the use of all congressional authorities available to us, including the power of 'inherent contempt' and impeachment hearings, to address these new allegations, find the truth and protect our national security."

— Excerpt from the WashPost op-ed by the 7 Democrats

Minnesota Democratic Reps. Dean Phillips and Angie Craig said later Monday that they would support impeachment against the president if the Ukraine allegations were proven to be true.

Connecticut Democratic Reps. John Larson and Rosa DeLauro said they would support impeachment proceedings if Trump's administration tried to prevent Democrats from investigating the Ukraine claims.

Rep. Debbie Dingell (D-Mich.) appeared on MSNBC's "The Last Word with Lawrence O'Donnell" to explain why she supported an impeachment inquiry.

Go deeper:

Editor's note: This article has been updated with new details throughout.