She pauses for dramatic effect, then laughs. No professional runner in her marathon prime would do that, certainly not someone like Flanagan who appears poised for more record-breaking success. But the joke reveals how much the Boston Marathon means to Flanagan, how it took hold of her young imagination and never loosened its grip.

“In my heart, I would feel complete winning Boston,” she said. “I would feel very fulfilled with my career. I would have exceeded all expectations. I have an Olympic medal. I’m a three-time Olympian. I have all these track records. Then, to win Boston, what’s better than that? Retiring wouldn’t happen because I love running so much. I want to continue and see what I can do.

“But if someone said, ‘If you win Boston, you have to retire tomorrow.’ I’d say, ‘OK, I’ll take that deal.’ ”

That thinking comes naturally from growing up in Marblehead and watching the Marathon on Patriots Day. In middle school, Flanagan cheered elite runners, and her father, Steve, from Boylston Street. She was captivated by the spectacle. Flanagan dreamed of striding down the historic homestretch, though running 800 meters seemed a long distance back then.

Making her Boston Marathon debut Monday as one of 18 elite women is a “full circle” moment for Flanagan. And it could be much more.

Flanagan will arrive at the starting line a strong contender for the women’s title. The 2008 Olympic bronze medalist in the 10,000 meters and American record-holder in the event (30:22:22) has the speed and, after years of marathon-specific training, the strength and endurance to cover a fast start, midrace surge, and sprint finish. Flanagan is capable of battling the Kenyans and Ethiopians down Boylston Street and becoming the first American champion since Lisa Larsen Weidenbach (now Rainsberger) won in 1985.

“It would be mind-blowing,” said Flanagan, of winning and ending the American drought. “It would be a life-changing moment. That’s why I have to remind myself to not let it get the best of me and not let the moment overwhelm me.”

Leading up to the Marathon, Flanagan talked regularly with her father, who ran a personal best of 2:18:36 at the Fiesta Bowl Marathon in the late 1970s and 2:20:42 on the Boston course in 1980 for 23d place. Steve Flanagan constantly reminds his daughter to “stay above the hype.”

Still, with three marathons on her résumé and nearly four years of marathon-focused training under coach Jerry Schumacher, Flanagan believes the timing is right for a big Boston debut. After all, she’s waited a long time for this moment, by her calculation 17 years since her middle school days.

“Hopefully, it’s delayed gratification,” said Flanagan. “I’m not a veteran by any means, but I definitely have learned a lot about myself and how to approach the marathon. Hopefully, I can knock it out of the park.”

Schumacher believes the wait will be worth it.

“I’m confident that Shalane can run the marathon in any way that it’s presented and be a factor,” said Schumacher. “Whether or not it’s her day, we’ll find out. Whether or not she wins, nobody has that answer. But we work really hard to be in the game. So, when the time comes, we hope it’s our day. If it is, I have a feeling the city of Boston will be pretty excited.”

Putting in the work

The Santa Fe Trail starts 7,250 feet above sea level, then drops nearly 500 feet over several quad-punishing miles. Tracing the eastern edge of the Front Range, the sandy path rolls through clusters of evergreen trees, high plains, and Air Force Academy territory. Pikes Peak looms in the distance as several sharp inclines test tired legs and lungs. Imagine the Boston Marathon course transported from paved streets to rugged, high-altitude Colorado. This winter, Flanagan and training partner Kara Goucher did exactly that.

With her blond ponytail rhythmically swinging side to side, Flanagan cut a lean, fast figure along the Santa Fe Trail. She favored the route because it simulated what she will experience Monday. And from a childhood immersed in the Boston Marathon, Flanagan knows Boston is as much about the legendary course as the competition.