The candidates are
part of a new wave of female veterans who want to be on Capitol Hill after the 2018 Midterms in November.
Currently just four of the 535 sitting senators and representatives are women who served in the military.
But in this cycle no fewer than 32 have run for office.
The numbers are tilted towards the Democrats, with around two thirds of such candidates fighting against President Donald Trump's Republicans.
Speaking to the Sunday Telegraph, all three women - who are running as Democrats - suggest that a sense of duty mixed with concern over Trump lies behind the trend.
Sullivan, 38, spent five years in the US Marine Corps, including deployments in Japan and Iraq.
She earned two medals for her service and later served as former President Barack Obama's assistant secretary on veterans affairs.
It was her concerns about the state of America after Trump's victory that convinced her to enter the political fray, seeking the congressional seat in New Hampshire's 1st district.
"Our country faces a crisis of leadership. We're at an unprecedented moment," she said.
"I've fought for our country, put my life on the line for our country. But I've never seen a moment facing our country quite like now."
For Houlahan, 51, it was a sense of duty passed down from generations of family in the military that convinced her to run.
Her father and grandfather both had careers in the navy.
She spent three years as an air force engineer at the end of the Cold War, helping design the system that sent alerts if a nuclear missile was on its way.
After Trump's 2016 election win, her father was left in tears.
Her daughter, who is gay, felt her own country had become unrecognisable.
"It was the beginning of a process of asking myself what I can do to be helpful," said Houlahan, who decided to stand for the seat in Pennsylvania's 6th district.
Keith, a 49-year-old former naval lawyer, spent much of the Nineties defending sailors who were facing everything from expulsion to discrimination cases.
She is running for Florida's 18th district and she hopes her background can overcome the gendered slurs that Hillary Clinton faced in 2016.
"How many times was Hillary's toughness or assertiveness or unflappability characterised in a negative light?" she asked.
"As a veteran you are expected to be strong. So when you show that quality, people are far more forgiving of women who were in the military than who are not."
Whether Sullivan, Houlahan and Keith are in Congress come Christmas remains to be seen. But the trend they are helping fuel shows little sign of abating.
