Despite a string of disappointments at 26.2 miles, Nick Arciniaga never felt discouraged. He believed his experience and training were carrying him toward a breakthrough race, and he promised himself he wasn’t going to let anything slow him down in Sunday’s Twin Cities Marathon.

When Arciniaga’s hamstring began to ache only 11 miles in, he paced himself carefully, taking strength from the jubilant crowds along the route. And when Josphat Boit engaged him in a final duel with 400 meters to go, Arciniaga gritted his teeth and dug in to seize the first marathon victory of his career. The California native outsprinted the Kenyan-born Boit to win in 2 hours, 13 minutes, 11 seconds, claiming the U.S. men’s marathon title and a $25,000 winner’s purse.

Boit finished only 3 seconds behind, and Shadrack Biwott placed third in 2:13:25. Sergio Reyes, the 2010 Twin Cities Marathon champ, finished fourth in 2:13:34 as the top four men were separated by only 23 seconds. Former Minnesota resident Annie Bersagel won the women’s title and the U.S. championship in 2:30:52.

It was the first U.S. championship at any distance for Arciniaga, 30, who lives in Flagstaff, Ariz. He beamed as he crossed the finish line with arms raised, finally achieving the triumph that had eluded him in 12 previous marathons.

“I’m elated,’’ he said. “My leg is hurting, but I feel great. To be able to battle and run with the front group in a really tactical race is a huge victory for me from a mental standpoint.

“It was championship-style racing for sure, with everyone trying to be patient and have the best strategy for themselves. The last 400 meters, I was just trying to go all out and not think about my leg hurting.’’

The 32nd edition of the race was run under ideal conditions. As runners toed the starting line at the Metrodome, temperatures hovered in the mid-40s, with intermittent sunshine brightening the course for the elite field. A light rain began falling later in the morning, when most of the 8,849 finishers were streaming across the finish line in front of the State Capitol.

Arciniaga’s strategy was to remain relaxed over the first 13 miles, tucking into the middle of the lead pack as it snaked out of downtown Minneapolis and around the lakes. His first test came when his hamstring started to hurt as the field approached Lake Nokomis.

After cursing his bad luck, Arciniaga realized he needed to quickly get his mind right if he was to stay in contention. Boit strode out from the pack as it skirted the lake and briefly held the lead, but the group of about 15 runners picked up the pace, closing the gap. Arciniaga stayed in their midst, occasionally dropping back a bit to ease the workload on his aching leg.

The lead group dwindled to five runners as it approached the Franklin Avenue bridge to cross the Mississippi River. On his way up the hill along Summit Avenue, Arciniaga focused on short-term goals, starting with being the first to reach the 24-mile mark.

“I was trying to motivate myself,’’ he said, “to stay in it and fight.’’

He did grab the lead, only to see the others pull even. At mile 25, Arciniaga again broke away, until Boit joined him for the final showdown.

“It was intense,’’ said Boit, who ran for Arkansas and won the 2006 NCAA title in the 10,000 meters. “You didn’t know who was going to win. I was nervous at that point; I didn’t know what I had left, and my legs were feeling really tired. But I wanted it really bad.’’

So did Arciniaga. His résumé includes top-15 finishes at several prestigious races, including the Boston, New York and Chicago marathons. Sunday’s hard-fought victory, he said, gives him hope that the best is yet to come.

“The last 400 meters, there were so many people cheering my name, it made it feel like everyone was pulling for me,’’ he said. “This means a lot, being able to come out here and perform like I wanted to. It’s a great feeling.’’