WASHINGTON — President Joe Biden’s most likely path to re-election is a narrow one that relies on the same three states that gave Donald Trump the Oval Office in 2016 and then yanked it away from him in 2020 — Pennsylvania, Michigan and Wisconsin — along with a single electoral vote from an Omaha-based congressional district.

Put another way, if Trump takes any of the Big Three Rust Belt states in November, it is probably an indication that he has won back the White House. Less than five months from Election Day, they comprise the real battleground, according to many operatives in both parties.

“That’s the must have,” said Faiz Shakir, a Democratic strategist who managed Bernie Sanders’s 2020 presidential campaign.

But it is difficult for any campaign to abandon states where the boss has won, or come close, before. That’s particularly true at this point in the race, when campaign aides believe there is still time for their efforts to affect public opinion, and in an election year in which the stack of Democratic-held electoral votes has been reduced by a recent census. They also know that they can’t force the opposition to spend precious campaign cash in states they have left for dead.

So, in addition to the Big Three, Biden’s high command is deploying resources to Georgia, Arizona and Nevada, where he prevailed in 2020, as well as North Carolina, where Trump won by about 1.3 percentage points.

Right now, most public polls are showing Trump leading in those states by larger amounts than in Michigan, Pennsylvania and Wisconsin, where surveys tend to be closer.

Biden aides say it is too early for triage.

“Today, we see across all those places a number of pathways” to reach 270 electoral votes, Dan Kanninen, the battleground states director for the Biden campaign, said. He described a strategy of flooding closely contested states with staff, buying ads and sending Biden and his surrogates to talk to voters in order to move the numbers.

Rep. Ro Khanna, D-Calif., a co-chair of Biden’s campaign, declined to rule out Biden repeating victories in Georgia, Arizona and Nevada — or finding a way to flip electoral votes into his column in North Carolina — but he emphasized the importance of the Rust Belt.

“We need to double down on Wisconsin, Michigan and Pennsylvania,” he said.

Biden and his White House crew — First Lady Jill Biden, Vice President Kamala Harris and Second Gentleman Doug Emhoff — have been to Michigan a dozen times collectively since his re-election campaign launched last year, according to an NBC News tally. The group has accounted for 10 trips to Pennsylvania and Wisconsin, while they’ve gone to Georgia eight times, Nevada and Arizona seven times and North Carolina five times, according to the NBC News analysis.

The first lady plans to travel to Wisconsin Thursday, where she will give an early afternoon campaign speech in Green Bay. The city is the government and population center in Brown County, one of the nation’s most important swing areas. From there, Jill Biden plans to fly to Duluth, Minn., for a speech in a state that her husband won in 2020 but that the Trump campaign has earmarked as a pickup opportunity. On Friday and Saturday, she will campaign in Nevada and Arizona.

The campaign’s decision to send her to Minnesota suggests that there is at least some concern in Biden’s circles about Trump’s inroads in a state Republicans haven’t won in more than half a century. It has as many electoral votes as Wisconsin — 10 — but most strategists believe it is more Democratic-leaning than any of the Big Three.

By himself, Trump has held seven campaign events in Nevada, six apiece in Michigan and Pennsylvania, three each in Georgia and North Carolina, two in Wisconsin and one in Arizona, according to an NBC analysis of his travel. His schedule was constrained, he has said, by the weeks he spent in a New York courtroom before he was found guilty on 34 counts related to falsifying business records as part of a scheme to help his 2016 campaign by covering up an alleged affair that he denies.

Trump is scheduled to appear at a rally in Detroit on Saturday and one in Racine, Wisconsin, on Tuesday. His campaign declined to make aides available to discuss their battleground strategy.

Because Democrats hold the White House, it would be natural for them to play more defense and for Trump’s out-of-power Republicans to go on offense in a wider set of states. There simply aren’t many — or perhaps any — realistic targets for Biden outside the states he captured in 2020.

Electoral math has become more complicated for Biden because reapportionment following the 2020 census took a net of three electoral votes away from states he won that year — including one each from Michigan and Pennsylvania — and moved them into states that favored Trump. Had Biden lost Georgia, Arizona and Nevada in 2020, and kept everything else, he would have accumulated 273 electoral votes. Now, that figure is 270 — the exact number necessary to win the presidency.

Enter Nebraska. It is one of two states, along with Maine, that award an electoral vote for each congressional district a candidate wins. Statewide, Nebraska voters have overwhelmingly favored Republican presidential candidates in recent elections. But Biden won the Omaha-based 2nd Congressional District — and its single electoral vote — in 2020.

It is conceivable that the election could come down to that single House district, which Barack Obama, Mitt Romney, Trump and Biden each one once in the last four election cycles.

If Biden keeps the rust belt trifecta but loses Georgia, Arizona and Nevada, a Trump win in the Omaha district would result in a 269-269 tie that would force the election to a vote of each state in the House. By winning the Big Three plus Omaha — or Nevada, Georgia or Arizona — Biden would win outright.

Khanna said there’s something “uniquely compelling” about Biden and his economic message in the Rust Belt states, adding that they represent “the clearest path to 270 electoral votes.”