Dunham first announced her plans to stump for Clinton last month after interviewing the Democratic candidate for her newsletter, Lenny Letter.
The Girls creator traveled to Boston; Manchester and Portsmouth, New Hampshire; Chicago; and Iowa City and Des Moines, Iowa, with her best friend Audrey Gelman as part of the campaign.
"I never imagined I would be traveling to four or more cities a day to spread the word on why I vote, why you should too, and why I'm supporting Hillary Clinton's bid for the presidency," Dunham, 29, wrote in her account of the trip. "But when the lady asks, I answer."
She continued, "I was never going to see the change I wanted to if I were half-hearted about showing up to the polls and half-hearted about saying what I believed in."
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The actress first spoke to supporters in Boston, where she met up with U.S. women's soccer star and fellow Clinton supporter Abby Wambach.
Both women continued on to New Hampshire, before they parted ways for Dunham to continue on to Chicago and eventually Iowa.
"In Des Moines my event was at a very stylish, Portlandia-esque silkscreen and design studio, where I got a chance to meet Planned Parenthood president Cecile Richards's daughter, Lily, the director of communications for the campaign in Iowa," Dunham wrote. "I was really thrilled to be making the rounds directly after Planned Parenthood endorsed Hillary – their first primary endorsement in their hundred-year history."
Dunham shared several images from the campaign trail (there were plenty of outfit changes) alongside her story before ultimately addressing why she supports Clinton for president.
"I believe that nothing will send a stronger message to America and the world at large than electing a competent, experienced, and brilliant woman to the highest office in the land," she wrote. "Our first female president would send a message that we are here. We are ready to lead. In fact, she has been leading all along."
She also addressed implications that she supports Clinton only because of their shared gender, something she called "estrogen blindness."
"The fact is, there are plenty of women whose politics horrify me, just as there are plenty of men who I would love to see in elected office," Dunham wrote. "My gender doesn't prevent me from making cogent decisions about who to vote for: In fact, my gender only informs those decisions in a powerful way."