Exactly half of American adults polled in late March by the Associated Press and the National Opinion Research Center said they believed the country was heading in the right direction.

That may not sound huge — a 50-50 split — but it’s the most optimistic finding since the AP-NORC poll started asking that question in 2015.

Go back further: The NBC-Wall Street Journal poll has asked that same question for decades. The last time it found an even split was, briefly, in the spring of President Obama’s first year in office. And the last time a clear majority of Americans thought the country was headed the right way? That was in 2003.

Even when Americans felt confident about the economy a year ago, before the pandemic disruption took hold, divisions over other aspects of President Trump’s tenure left a majority saying that the country was on the wrong track.

So it’s fair to say, based on that question and others, that President Biden is riding a wave of optimism that goes beyond what his last two predecessors enjoyed.

This wasn’t what most analysts forecast after Biden’s election. Democrats lost seats in the House, and their narrow majority would make passage of any legislation difficult, many analysts expected. Tensions between the Democrats’ energized progressive wing and Biden’s more moderate White House threatened to tie the party in knots.

Whatever did pass the House appeared doomed in what was, back in November, still a Republican-majority Senate. The GOP seemed in good position to repeat the strategy it had used against Obama in 2009 — frustrating his legislative efforts as much as possible while campaigning against gridlock in Washington.

Then, in January, Democrats gained control of the Senate by winning the twin runoff elections in Georgia, which increasingly seems to be the most consequential Senate result in decades. Handed a narrow majority in both chambers, the party has demonstrated notable discipline while Republicans have fallen to quarreling among themselves.

Biden’s $1.9-trillion COVID-19 relief package won relatively swift passage in Congress and has proved broadly popular with voters, including a significant minority of Republicans.

Meanwhile, vaccination numbers are rising fast; a majority feels we’ve left the worst of the pandemic, despite surges in some states, and the economic picture has improved markedly.

On Thursday, the Standard & Poor’s 500 stock index closed above 4,000 for the first time, the sort of stock surge about which Trump used to crow.

On Friday, the Labor Department reported that the economy had generated 916,000 new jobs in March, the strongest gain in seven months, and the unemployment rate had ticked down to 6%.

At the White House, Biden took the opportunity to bask in good news.

“In the first two months of our administration, I’ve seen more new jobs created than in the first two months of any administration in history,” he said, adding that “we have a long way to go.”

Republicans, of course, will seek to deny Biden credit, just as Democrats insisted before the pandemic that Trump was merely riding a wave of prosperity generated by Obama’s policies.

“We are about to have a boom,” Senate Republican leader Mitch McConnell of Kentucky said last month after the Senate passed the relief package. “And if we do have a boom, it will have absolutely nothing to do with this $1.9 trillion.”

Party activists love such arguments; other voters ignore them. The growing weight of partisanship has reduced the bounce an incumbent can get from improving conditions, but the person in office still gets the benefit of good news and the blame for bad.

Biden knows that, and he’s making the most of it.

On Wednesday, the president traveled to Pittsburgh and unveiled the next chapter in his economic plan, a bill to spend roughly $2 trillion repairing aging roads and bridges, replacing lead water pipes, expanding ports, laying cable for broadband, building housing, fostering electric vehicles and converting utilities to renewable power. A third chapter, focused on aid to families, will come this month, officials say.

To shore up support among any anxious Democrats — and perhaps to prod Republicans to come to the negotiating table — the president and his aides have sent a clear message: Voters liked the last bill; they’ll like this one, too.

In Friday’s remarks, Biden said the plan would create 19 million new jobs — “good jobs, blue-collar jobs, jobs that pay well,” he said, emphasizing that 90% of the infrastructure jobs created would not require a college degree.

While Republicans have attacked the amounts Biden proposes to spend, voters don’t seem put off. On the COVID package, at least, evidence suggests they see the size as a feature, not a bug.

In late March, the polling firm YouGov tested that. It divided a survey in two, asking half the respondents if they supported “the COVID-relief legislation recently passed by Congress” and the other half if they supported “the $1.9-trillion COVID-relief legislation recently passed by Congress.”

They expected support would drop when people were reminded of how much the bill cost. The opposite happened: Among Americans of both parties, the bill was somewhat more popular among those asked the question with the price tag attached.

“When it comes to the way Americans perceive COVID-19 relief,” YouGov’s Mark Blumenthal wrote, “bigger was better.”

That may not hold true with the next piece of legislation, which aims to fix long-standing problems, not deal with the impact of a pandemic emergency.

Republicans have returned to attacking the bill as too pricey and unfocused. Biden’s plan offers “blind faith in government spending and regulations, blank checks for left-wing ideologues, and far less money and freedom for families, small businesses, and workers,” House Republican leader Kevin McCarthy of Bakersfield said in a statement.

That may work, but voters like the idea of improving the nation’s infrastructure. That’s one reason Trump kept talking about a big infrastructure bill, although he never produced one. As for Biden’s proposal to pay for the bill by increasing corporate taxes, polls repeatedly have shown that voters like that, too.

None of this guarantees smooth sailing for Biden.

Recall that surge in optimism in Obama’s first spring: By summer, it had disappeared, ground down by high unemployment and political disputes.

The same could happen again. Surging COVID caseloads might outrun the pace of vaccinations, setting off a fourth wave of deaths. Or the new spending could trigger a sustained bout of inflation, threatening the economy.

For now, however, those risks remain hypothetical. In reality, the new administration has achieved its early goals and is now reaping some benefit. Success breeds success in politics, and Biden has moved quickly to take advantage of it while it lasts.