Robert Ashby of Brunswick will be inducted into the Maine Running Hall of Fame this fall, so his road race sample size is a large one.

The Maine Marathon, Half Marathon and Marathon Relay remains a favorite for Ashby, 48. Two years ago, he ran the final steps of the marathon hand-in-hand with his son Cameron, then 13, who joined his dad near the finish of the race.

About a minute later, Ashby’s wife, Fran Smith, and their daughter Micaela did likewise in the half marathon.

“That’s something that’s special about this race,” Ashby said. “It’s a nice family event.”

Sunday marks the 25th annual edition of the races, which include a marathon relay along with the full and half marathons. Each is scheduled to start at 7:45 a.m. on Portland’s Baxter Boulevard near Pedro Field. Everyone runs together for the first 6.5 miles before the half marathoners round a cone in Falmouth and head back to Portland. Marathon and relay runners continue along Route 88 to Yarmouth before retracing their steps for the return journey along the Back Cove.

“It’s incredibly well organized and it’s just a great atmosphere,” said Ashby, the runner-up last year to two-time winner Evan Graves of Caribou.

“You’ve got people cheering on the entire course. You’ve got great scenery all the way out. Usually you get some leaf changing. I’ve run a lot of different marathons over the years and I always seem to go back to (the Maine Marathon) because it’s just very well put on.”

As of Wednesday afternoon, 875 runners had registered for the marathon and 2,167 for the half. The relay was capped at 125 teams.

Participation in the marathon peaked in 2014, the only year with more than a thousand finishers (1,019). Last fall, 850 runners completed the full 26.2-mile round trip. Not since 2008 had so few finished the marathon, a trend that reflects a national decline. According to Running USA’s annual report, there were 8 percent fewer marathon finishers in 2015 than in the peak year of 2014.

The Maine Marathon traditionally has been the state’s largest. In May, however, the Maine Coast Marathon in Kennebunk and Biddeford had a record-high 874 finishers. Maine’s most popular half marathon is the the Old Port Half in Portland, which had 2,889 finishers in July.

Even so, this weekend remains a highlight of the state’s road-racing calendar. Chris Harmon, 28, of Portland will attempt his third marathon Sunday. He was second in his 2014 debut and this April was the top Mainer in the Boston Marathon.

“I grew up in Portland,” Harmon said. “I’ve run Back Cove just about every day of my life, so it’s familiar. And it was my first marathon, so it’ll always be special to me.”

Now a lawyer, Harmon won the summer’s Back Cove Weekly 5K series as well as the Sea Dogs Mother’s Day 5K and the recent Trail to Ale 10K.

His main competition Sunday is likely to come from former University of Maine teammate Spencer McElwain and Falmouth transplant Michael Gordon. All three belong to the Dirigo Running Club.

Neither Graves nor three-time defending women’s champ Leah Frost of Glover, Vermont, is entered, leaving each field wide open.

As for the half marathon, Falmouth native Jonny Wilson plans to take a run at the course record of 1:06:56 set by Ellsworth’s Louie Luchini in 2009.

Wilson, 28, has broken 66 minutes in the half five times, and in March ran 1:06:13 in New Bedford, Massachusetts, finishing in second place by one second.

“My first goal is try to win,” Wilson said by phone from Arizona, where he spends most of his year. “And then to try to get under Louie’s time would be a big deal, and if I felt good enough, to try to get under the old race record.”

That would be the 1:06:23 by Jose Rocha of Peabody, Massachusetts, on the old course in 1994. Organizers changed the route seven years later.

“There’s such a great history behind the race and behind Maine distance running,” said Wilson, who earns a living as an online running coach. “So to be a part of that this year is pretty cool. If I could not only come out with the win but also get the record, that would be a pretty cool thing to do.”

Sunday’s event edition marks the last for race director Howard Spear, who is turning the reins over to Bob Dunfey after 18 years at the helm.

“It’s a lot of work,” Spear said. “I’m still going to stay on the (race) committee. I just want to let someone take over all the calls.”