Though President Donald Trump’s term has 34 months remaining, it’s already more than halfway from Iowa’s 2016 presidential caucuses to the next ones. Some two dozen Democrats — and a handful of Republicans — are eyeing 2020 candidacies.

Heading the potential Democratic field are two well-known septuagenarians, Joe Biden and Bernie Sanders. More than a dozen senators, representatives and governors are mulling bids. One, Maryland Rep. John Delaney, is formally running.

In addition, some relatively unknown non-Washington figures are weighing the odds that lightning can strike, as it did in 1976 for former Georgia Gov. Jimmy Carter. Some will likely run in a year the Democratic nomination will be appealing and the race wide open.

Here are five of the most interesting:

Gov. Steve Bullock of Montana, 51, a Democrat who has succeeded in a red state and is highly regarded by his peers, is making his first Iowa visit next weekend, attending an event for veteran Attorney General Tom Miller.

“I’m excited to go out there for a couple of days, but, by and large, I got the greatest job, certainly in Montana, I think in America,” Bullock said. He called his current job, which runs until 2020, “all consuming.” While mainly focused on “the weeks and months ahead,” he added that he is “certainly not sure what the future will hold in that respect.”

Besides being virtually unknown, Bullock lacks an ideological or geographic base for a presidential bid.

Pete Buttigieg, 36, the openly gay mayor of South Bend, Ind., recently added Iowa to states where his political action committee is helping fellow Democrats.

The former Rhodes scholar and Afghanistan vet made a strong impression among party insiders in his unsuccessful 2017 bid for the party chairmanship and speaking to the Progress Iowa Corn Feed last September in Des Moines.

“Things are kind of wide open in a way that hasn’t been true in a long time,” he told Politico’s Off Message podcast. “I think it shows that there’s at least curiosity, if not appetite, for what a newer generation of leaders is going to look like.”

He may be the longest of the long shots. One reason running nationally is attractive is because Indiana is so Republican it’s hard for Democrats to win statewide office; “Mayor Pete” lost a 2010 race for state treasurer.

Former HUD Secretary and San Antonio Mayor Julian Castro, 43, who brings both local and national executive experience, sounds like a candidate, making clear on a recent New Hampshire visit he is giving serious thought to running.

He told NBC News he has “every interest in running,” and told his hometown San Antonio Express-News he’ll decide by the end of 2018. “I legitimately haven’t decided yet,” he said.

Touting his experience as mayor and a Cabinet secretary — and, though unstated, clearly inviting a comparison with Trump — he declared, “I’ve demonstrated an ability to work with both sides of the aisle” and shown “an ability to get things done and to make level-headed decisions.”

Like Buttigieg, home-state Republican strength makes national office a better bet than running statewide.

Former Missouri Secretary of State Jason Kander, 36, easily the most active potential 2020 Democratic hopeful, will make his 12th Iowa visit this month and headline a major New Hampshire Democratic fundraiser.

After narrowly losing a 2016 Missouri Senate race, he formed the group Let America Vote, to fight Republican efforts to curb voting, giving him a ticket to travel widely. Now he has created organizations — staffed by presidential campaign veterans — in five states, including the first three states on the nominating calendar.

Still, it’s hard to believe that Democrats would pick someone whose highest elected office was secretary of state in an election that may spotlight Trump’s inexperience and ineptness.

Mitch Landrieu, 57, the outgoing New Orleans mayor who removed four Confederate monuments, likens Trump to David Duke, the neo-Nazi he once fought in Louisiana’s Legislature.

In his forthcoming book, “In the Shadow of Statues: A White Southerner Confronts History,” Landrieu writes that, while “Trump is not a Nazi,” he “has courted white nationalists as Duke did and like Duke, he speaks and tweets a fountain of lies, lying as naturally as normal people try to be truthful.”

Of the five, Landrieu seems least likely to run. He has not visited early states and told a Bloomberg breakfast he doesn’t intend to be a candidate, but added, “Things could change.” He has served 30 years in the Legislature, as lieutenant governor and as mayor, and Democrats have a history of favoring moderate Southerners, like Jimmy Carter and Bill Clinton.

To win the 2020 nomination will take a boatload of money and a willingness to spend much of 2019 seeking the support of activists in Iowa, New Hampshire, South Carolina and Nevada. The race is wide open for a newcomer, but the barriers are high.

Carl P. Leubsdorf is the former Washington bureau chief of the Dallas Morning News. Readers may write to him via email at: