Tulsi Gabbard’s decision not to seek reelection to Congress and instead focus on her presidential campaign opens an opportunity for familiar and lesser-known potential candidates who might want to run in 2020 to represent rural Oahu and the neighbor islands.

In the aftermath of Gabbard’s announcement, the list of people who might consider running to represent Hawaii’s 2nd Congressional District suddenly ballooned Friday to include Honolulu Mayor Kirk Caldwell, former U.S. Rep. Charles Djou, former Kauai Mayor Bernard Carvalho, former state Sen. Jill Tokuda, current state Sen. Donna Kim and state Reps. Chris Lee and Stanley Chang, among several others.

“It’s always tough to beat an incumbent,” said political analyst Colin Moore, a University of Hawaii associate professor of political science. “Now it’s going to be an even more exciting race than I expected.”

Until Gabbard’s announcement Thursday, her main competitor in the Democratic primary was state Sen. Kai Kahele, who represents his hometown of Hilo and serves as majority floor leader.

On Friday, Kahele still considered himself the favorite and declined to speculate on who might now choose to run against him.

“I don’t think it changes the dynamics of the race,” Kahele said. “Fundamentally, for our campaign, nothing changes. You can’t just parachute into Congressional District 2 out of political convenience.”

On Friday, though, even Caldwell’s representatives would not rule out the possibility.

Term limits prevent Caldwell from seeking a third consecutive term as mayor in 2020.

“At this point the mayor is focused on doing the best job he can as mayor for the balance of his term,” said Lex Smith, campaign chairman of the Caldwell campaign. “He’s mostly focused on accomplishing the goals that he has as mayor. But he is keeping his options open. I suppose that could include Congressional District 2.”

State Rep. Chris Lee (D, Kailua-Lanikai-Waimanalo) had no thought of challenging Gabbard if she chose to run again. “I hadn’t been planning on it,” said Lee, who is serving his sixth term in the House.

That changed with Gabbard’s announcement.

“I woke up to about 100 text messages and calls this morning about it,” Lee said Friday. “It’s something that, maybe at this point, I definitely have to do some soul-searching and thinking about.”

Councilwoman Kymberly Pine, who represents the Leeward Coast, said she also had been contacted by multiple people gauging her interest.

Asked whether she’ll enter the race, Pine was adamant.

“No, no, no,” Pine told the Honolulu Star-Advertiser.

“No one could beat Tulsi Gabbard if she ran,” said Pine, who was a colleague of Gabbard’s when they both served in the state Legislature.

But with Gabbard’s decision to not seek reelection, Pine expects the race will soon become “a very crowded field. … I would imagine that a lot of people, even Mayor Caldwell, would be looking at that seat.”

Moore said some of the most familiar names being talked about — including former Honolulu Mayor Mufi Hannemann, who lost to Gabbard in 2012 — face challenges of being Oahu- centric or too closely aligned with Hawaii’s Democratic Party.

Lesser-known officials — including a handful in the Legislature — don’t have as many “unfavorables.” But they also don’t have high name recognition and have not been building a neighbor island political base, Moore said.

“On the neighbor islands, being the mayor of Honolulu isn’t a point in your favor,” Moore said. “But I wouldn’t be surprised if Mufi got in this race.”

Hannemann, president and CEO of the Hawai‘i Lodging and Tourism Association, said in a text to the Star-Advertiser, “I have not considered a run for this office as presently I find my work and other responsibilities very fulfilling enabling me to continue to positively contribute to our community.”

Anyone running for Gabbard’s seat could learn many lessons from her, Moore said.

“She was fresh, she was independent,” Moore said. “She’s such a unique character. Like Tulsi, you can go far by running against the Democratic establishment here — showing independence from the power brokers downtown. Especially on the neighbor islands and rural Oahu, that plays well.”

Like Gabbard, Kahele highlights his military serv­ice. He is an 18-year combat veteran aviator who is a lieutenant colonel serving in the Hawaii Air National Guard.

Since he began campaigning 10 months ago, Kahele has raised more than $600,000 and won the endorsements of former Govs. John Waihee, Ben Cayetano and Neil Abercrombie, along with Honolulu Council Chairman Ikaika Anderson.

Kahele’s late father, Gil, was a longtime Democratic Party activist and campaign supporter of many of Hawaii’s leading Democrats before he himself became a state senator.

Todd Belt, a former University of Hawaii-Hilo political science professor who is now director of the political management master’s program at The George Washington University, met Kai Kahele several times and calls him “an impressive politician” who had a good chance to defeat Gabbard in a head-to-head race.

Gabbard had put “everything into her presidential race,” Belt said. “So it’s really easy to say, ‘You’re out of touch. It’s your ego and your ambition that’s getting in the way of serving your congressional district.’”

At the same time, Belt said Kahele has been building a strong political apparatus.

“Kai Kahele learned from his dad how to run a good campaign,” Belt said.

But Belt said Kahele is also “a pretty impressive politician” on his own.

“He has a presence and an authority when he speaks that very few politicians in Hawaii have,” Belt said.

Kahele called Hawaii’s 2nd Congressional District “arguably one of the most complex congressional districts in the nation.”

“It’s spread over eight islands,” he said. “We’ve been working hard going island to island, community to community, neighbor to neighbor. You can’t drive there. You can’t take a bus.”

It’s in the 2nd Congres­sional District where “some of the most divisive issues in our state right now” are brewing, such as ongoing protests at Mauna Kea, Waimanalo and Kahuku, Kahele said.

“There is an energy in the 2nd Congressional District that I haven’t seen for quite some time,” Kahele said. “It’s exciting.”