On Twitter, Duckworth said she made her newborn, Maile, had a jacket "so she doesn't violate the Senate floor dress code (which requires blazers)".
Duckworth's vote was her first appearance in the Senate since giving birth. It's the first Senate rule change since 1977, when service dogs were first allowed on the floor. Wednesday's vote was thrilling, and expected. (Until then, children and family members of Senators remain completely barred).
"I think it would do us good, every once in a while, to see a pacifier next to the antique inkwells on our desks, or a diaper bag next to a brass spittoon that hasn't been used in decades", he said. Or adhere to a dress code?
There was more, voiced privately, Klobuchar said - including whether Duckworth meant to change Maile's diaper or nurse her new baby on the Senate floor. But with 23 women serving in Senate, some 70 percent of mothers working in the United States and a midterm election looming, no senator was willing to publicly declare he or she was a "nay" on babies.
She gave birth to her second daughter, named Maile Pearl Bowlsbey, April 9.
Tammy spearheaded the initiative, not wanting to be away from her baby girl, but still seeking to carry out her duty as Illinois' duly elected Senator.
The chamber was built in 1859, and the cloakroom is hard to access from the outside for Duckworth, who lost both her legs when she served in the Iraq war.
"Yes, you can vote from the doorway of the cloakroom, but how is she going to get to the cloakroom when it's not wheelchair accessible?" she asked.More news: LeBron James scores Cavs' first 16 points, dominates Pacers
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This was a frequent question, Klobuchar noted.
"I think it's historic, I think it's incredible", Duckworth said. "We have plenty of babies on the floor", joked Sen.
"We could only wish we had 10 babies on the floor", Klobuchar fired back.
What if the baby cries?
Most senators, though, were supportive, Klobuchar said.
It's unclear how soon Duckworth might take advantage of the new rules.
The inspiration for the historic change of rules was Sen. "As tough as juggling the demands of motherhood and being a Senator can be, I'm hardly alone or unique as a working parent, and my children only make me more committed to doing my job and standing up for hardworking families everywhere".
She also thanked colleagues for passing the rule change.