She came to be known as the "Trump whisperer".
The 49-year-old New Jersey native, a lawyer and long-time Republican strategist and pollster, was Mr Trump's third campaign manager. Mr Manafort, a veteran lobbyist and powerbroker, was key in securing the billionaire's nomination at the Republican National Convention in July.
He had taken over in June from Corey Lewandowski, who, while credited with Mr Trump's early rise during the boisterous primary season, was seen as unable to rein in his candidate. Mr Lewandowski's motto, written on his office whiteboard, was "Let Trump Be Trump".
That may have helped the showman capture the attention of the Republican faithful, but as focus turned towards Ms Clinton, he needed to stay on message.
"She played a huge role," Ben Dworkin, director of the Rebovich Institute for New Jersey Politics at Rider University, told NJ.com. "She got him across the finish line. She convinced him to stay on message. She was more effective at managing Donald Trump than anyone else."
In fact, Ms Conway did what even his wife Melania seemingly couldn't: she put her foot down and revoked his Twitter privileges, in a bid to put an end to his infamous late-night rants.
One such volley, a 3am tweet directed at former Miss Universe Alicia Machado in which he urged followers to "check out [her] sex tape", was viewed as particularly crass and gave ammunition to the Clinton campaign.
"She fought to make him more disciplined, and every time it worked, Trump started surging," Seton Hall University political science professor Matthew Hale told NJ.com. "She also recovered and helped him recover when he went off the rails. That helped, and she will get credit."
When she took over in August, the Trump campaign was widely viewed as being in a slump, following a damaging week in which the nominee had feuded publicly with the Muslim family of a slain US soldier.
"I was troubled by the lack of professionalism from the trenches, but also encouraged by the arrival of Kellyanne at Trump Tower, who I think was the one figure in the long saga of the Trump campaign that Republican regulars like me thought, okay, there's an experienced hand at the wheel," conservative radio host Hugh Hewitt told The Washington Post.
In the same piece, Ms Conway described how her pitch in the final months was "joy". "He asked me if I can run this thing on August 12th, it was a Friday night," she said.
"One thing I said to him was, 'Let's see who Hillary Clinton is and what she's doing. And let's do what she won't do and be where she's not and can never be.' And I started out with the word 'joyful'. In other words, I said to him, 'You know you're running against the most joyless candidate in presidential political history. Are we campaigning or are we getting a root canal every day when she's out there?'
"I said, 'You're starting to look like her.' [He said,] 'No. I'm not.' And I said, 'There it is. Yes, you are.'"
Ms Clinton, she said, struck her as "somebody who's always caught unaware". "She was caught unaware by Barack Obama in 2008. She seemed to be caught unaware of Bernie Sanders's surge. [And I thought], we could catch her unaware again," she said.
"In the wake of President Obama's historic victory, I was curious and not so convinced that Hillary Clinton was going to be able to claim the same mantle toward history that he did. I've always thought for Hillary, the question is not, 'Would you vote for a woman?' It's 'would you vote for that woman?' It's Hillary. It's not a hypothetical."
With just over two months until Donald J. Trump is sworn in as the 45th president of the United States, the question is no longer hypothetical. What Ms Conway's role in the new administration will be is still however unknown..
But on Thursday, she confirmed that she had been offered a job in the White House.
In a fiery response to New York Magazine's Gabriel Sherman, who said she was telling people privately she was "reluctant" to give up running her polling business, Ms Conway said the report was "false".
"Could it be those 'sources' want the WH job I've been offered?" she tweeted.
