Honolulu is undergoing rapid and enormous change.

Countering homelessness continues to be a struggle, with city government playing a lead role. A development boom has seeded high-rises along the Kakaako waterfront, as well as huge subdivisions elsewhere in the urban district. An aging infrastructure groans under the pressure of a growing population.

Most significantly, the rail system under construction — at $7 billion so far, a much more expensive and complex enterprise than city leaders first presented — will run out of money before it reaches the planned terminus at Ala Moana Center, which it must do.

That last issue is really the crux of the mayoral race, and frustrated voters need to elect the candidate best prepared to move the project forward. Otherwise, rail will become a white elephant stuck at Middle Street.

Of the contenders, only Mayor Kirk Caldwell has developed the foundations of a workable plan to navigate the 20-mile system’s difficult fiscal future. He remains the best candidate to fulfill this core mission, and voters should return him to the Honolulu mayor’s office.

Caldwell is facing his stiffest challenge from Charles Djou, a former Honolulu City Councilman and U.S. congressman.

Djou, who served as chief critic of the project while on the Council, has fallen comfortably back into that role. He asserts that Caldwell stood on the sidelines and did not sufficiently fact-check cost projections and other project concerns. He said the incumbent, who once campaigned as the one who could “build rail better,” is accountable for what’s gone wrong.

Djou has a point, and Caldwell knows it. The mayor is now more aggressively using his own bully pulpit to challenge the fiscal assumptions about the project. And he is making overtures to developers and others who could play a part in a new financing scheme for the final third of the route.

Caldwell told the Honolulu Star-Advertiser editorial board about discussions with private partners who could share the costs as well as the benefit of some of the 21 planned rail stops. Voters must wait to see what comes next, but they at least know Caldwell’s endgame and that he is spurred to move ahead.

The same can’t be said about Djou’s plan. He told the editorial board that he would build the project to the limit of existing revenue sources. At that point, he said, there may be an opportunity to consider a switch to something like bus rapid transit, using the guideway as built, and finding a way to continue at grade. But he hasn’t put pencil to paper yet, not even in preliminary fashion, to cost out the possible alternatives.

The third front-runner, former Mayor Peter Carlisle, said he is committed to completing the system as designed — but offered little in financial planning.

On another issue, both Carlisle and Djou have faulted Caldwell, and rightly so, for allowing too much administrative oversight of the city Ethics Commission, which should be independent. The role played by the city’s Corporation Counsel in criticizing the work of Chuck Totto, the commission’s longtime executive director, and Totto’s eventual resignation under fire, cast a pall over a commission whose effectiveness depends on public trust.

On other fronts, however, Caldwell has done a credible job. He has engaged with nonprofits and others on projects to address the city’s homelessness crisis, generally attacking the challenge with more energy than the governor has done.

He has worked to incentivize landlords to accept homeless tenants, and has engaged the private sector to add units to current housing stock.

He has made progress on the rehabilitation of many of Oahu’s battered roadways and other elements of the city’s aging infrastructure.

The bottom line: Caldwell has the best prospects for making further gains in the coming four years — not only in completing the rail, but helping Honolulu function better overall. He deserves more time to do so.

HONOLULU CITY COUNCIL

In District 1 (Ewa Villages, Kapolei, Makakilo, Nanakuli, Maili, Waianae, Makaha),it’s a four-way race between incumbent Kymberly Pine, neighborhood board member Kioni Dudley, former Councilman Tom Berg and newcomer Marc E. Anthony.

Pine has represented her constituents well and deserves another term to tackle the thorny issues affecting West Oahu, including traffic congestion and homelessness. She has worked to improve access to the Waianae Coast Emergency Access Road, pushed for a new contraflow lane in Waianae and hosted job fairs and community forums, among other initiatives.

She advocates building rail transit to Ala Moana Center without raising taxes. On rail’s rising costs, Pine said “more needs to be done to reject all overpriced bids and to make construction companies explain their costs to the public” — and all Oahu residents should hold her to that.

Three other contested Council seats go straight to the general election ballot: In District 5, Kimberly Case versus incumbent Ann Kobayashi; District 7, Chace Shigemasa against incumbent Joey Manahan; and District 9, Emil Svrcina challenging incumbent Ron Menor.