Tammy Duckworth Is Battle Tested. Could She Help Joe Biden in His Biggest Mission?

Dan Milberg is a retired Army helicopter pilot who voted for Donald J. Trump in 2016, and does not wish to vote for him again. But before he can consider pulling the lever for former Vice President Joseph R. Biden Jr., he needs to know who his running mate will be.

“It might be someone too progressive,” said Mr. Milberg, who lives in Robertsville, Mo.

The one person who would put him at ease, Mr. Milberg said, is the pilot whose seemingly lifeless body he lifted from a helicopter in 2004, her legs blown off by a rocket-­propelled grenade not far from Baghdad: Senator Tammy Duckworth of Illinois.

It is not so much the event that indelibly marked both of their lives and earned Ms. Duckworth a purple heart that draws him to her, Mr. Milberg said. Rather, he continued, she “is moderate enough that I think she can be appealing.”

Ms. Duckworth is among more than one dozen women who have been considered by the Biden campaign to join his ticket, and she is among a smaller group asked to submit documents for vetting. But she is rarely talked up by Washington’s consultant class.