As a tumultuous primary season draws to a close, Democrats have opened up more than one path to winning control of the Senate, according to strategists in both parties and independent analysts, reshaping the battle on a map where Republicans still hold significant advantages.

Voters are uneasy about President Trump’s handling of the economy, and his unpopular war with Iran has driven increases in the costs of fuel, food and health services, putting Republicans on the defensive in states they once saw as much safer terrain.

The basic contours of the map remain challenging for Democrats. Holding 47 seats in the Senate, they must flip at least four to win a majority. At the same time, they are trying to defend seats in two states Mr. Trump won in 2024. And four of the six most competitive races are in states Mr. Trump won by double digits.

Republicans are also hoping that Democratic divisions in two important battlegrounds, Maine and Michigan, could help offset some of the political headwinds.

Mr. Trump himself has expressed concern about a pattern of Republicans not performing as well in cycles when he is not on the ballot. “Pretend, please, that I’m on the ballot,” he said at a rally in South Carolina on Friday, aiming to motivate his base.

But Mr. Trump’s approval rating is below 40 percent, unnerving Republicans, who worry that voters in the center will break for Democrats. And rank-and-file Democratic voters are plainly energized: They have been turning out in huge numbers for primaries.

Now the battle for the Senate, once seen as tilting heavily toward the G.O.P., is increasingly up for grabs.

Democrats Make Recent Gains

The National Picture

The latest show of Democratic strength came last week in conservative-leaning Alaska. Former Representative Mary Peltola, a Democrat who had recently fired a top aide and changed campaign managers, led Senator Dan S. Sullivan, the Republican incumbent, by more than five percentage points in the state’s nonpartisan primary, according to incomplete results.

“I haven’t seen that kind of energy for a Democrat in Alaska in decades,” said Senator Catherine Cortez Masto of Nevada, a former chair of Senate Democrats’ campaign arm. “Democrats are energized. You see it across the country.”

By Thursday, the Cook Political Report, a nonpartisan election forecaster, moved races in Texas and Iowa from “Lean Republican” to “Toss Up,” citing polling and the economic environment.

The shift grew the core Senate battlefield from four states — Alaska, Maine, Michigan and Ohio — to six, widening Democrats’ margin for error.

“It’s a 50-50 tossup,” said Douglas Heye, a Republican strategist. “Republicans are nervous. They’ve watched Trump’s numbers be a constant limbo contest of ‘How low can they go?’”

While Republican groups have a vast cash advantage over Democratic ones, individual Democratic Senate candidates are handily out-raising their Republican opponents in most of the key Senate races.

Alex Latcham, executive director of the top Senate Republican super PAC, the Senate Leadership Fund, said his party still had “advantages in the quality of candidates, in our message and in our ability to raise and spend resources.”

As of Friday, Republican advertising spending surpassed that of Democrats in all the top six races except for the one in Texas, according to the ad-tracking firm AdImpact. Democrats, whose national party is entering the fall in debt, argue that spending will not be decisive.

“The truth is that all the money in the world should not change the fact that Trump and the Republicans in Congress have made life much more difficult,” said Senator Kirsten Gillibrand of New York, chair of Senate Democrats’ campaign arm, adding: “People are fed up. And they’re exhausted. And they can’t afford anything. And they’re going to change who’s in charge.”

Alaska, Iowa and Ohio

Economic Conditions Challenge Republicans

By May, when the average gas price rose as high as $4.56 a gallon, Mr. Trump had dismissed the economic costs of the war with Iran, saying they were outweighed by national security interests.

“I don’t think about Americans’ financial situation,” he told reporters in mid-May. In a cabinet meeting later that month he declared, “I don’t care about the midterms.”

Gas prices have since dropped somewhat from their spring peaks, but they remain elevated, and the fallout from the fighting has spilled across the economy, driving inflation that has outpaced wage growth. Voters say they feel gloomy about the economy.

Some states at the center of the Senate battle have been hit hard.

In Alaska, the cost of a gallon of gas on Sunday was $4.82, roughly 70 cents above the national average, according to the AAA motor club.

The economic pressures have been enough to give Democrats hope in a state where Republicans feel their nominee, Representative Ashley Hinson, a skilled fund-raiser, is a particularly strong candidate.

The same economic forces are at play in Ohio, another agriculture-heavy state. There, Sherrod Brown, a former senator and a Democrat, is trying to stage a comeback and has out-raised Senator Jon Husted, the Republican incumbent, by an overwhelming margin.

Dale Butland, a Democratic strategist in Ohio, said the signs of deep voter discontent were plainly visible. “It’s bad here,” Mr. Butland said of economic conditions in Ohio. But politically, he added, “it’s all breaking now in our favor.”

Maine, Michigan and Texas

Candidate Concerns for Both Parties

In other areas of the country, Republicans see more encouraging signs.

In Maine and Michigan, Republicans say that primary season handed them relatively weak Senate opponents who they believe could lose in more Democratic-leaning terrain. In Maine, the candidate the party initially nominated, Graham Platner, was accused of rape a month after the primary.

Mr. Platner, who denied the allegation, exited the race, requiring Democrats in Maine to scramble to find a last-minute replacement. They settled on Troy Jackson, who finished third in Maine’s primary for governor in June.

Democrats have appeared to quickly coalesce behind Mr. Jackson, and some polls show him leading Senator Susan Collins, the Republican incumbent. But many in the party remain anxious about his electoral track record. And they are concerned that some Democrats captivated by Mr. Platner’s campaign may not turn out for a candidate who did not go through the normal primary process.

In Michigan, where Mr. Trump won narrowly in 2024, Democrats are rushing to heal the wounds from a bruising primary animated by personal attacks and fierce disagreements over Israel. Some Jewish Democrats in Michigan have declined to immediately back the nominee, Dr. Abdul El-Sayed, who spoke out forcefully against Israel during the primary.

The Republican nominee, Mike Rogers, who is trying to flip a Democratic-held seat, has already begun to issue appeals to disaffected Democrats. Dr. El-Sayed, a left-wing insurgent, is trying to defy a trend for activist progressives, who have tended to perform worse electorally than the rest of their party.

In Texas, on the other hand, Democrats believe Republicans offered them an opening by nominating Ken Paxton, the state’s scandal-plagued attorney general.

Mr. Paxton has been indicted on securities fraud charges (he reached a deal with prosecutors to avoid a criminal trial), has escaped an impeachment trial, has been accused of adultery by his estranged wife and was even caught on video years ago pilfering a prize pen.

Democrats have nominated James Talarico, a Presbyterian seminarian who has made his Christian faith a centerpiece of his campaign. The popular podcaster Joe Rogan once told him to run for president.

The contrast between the candidates has fed Democratic hopes and Republican fears that Texas might slip out of G.O.P. hands for the first time in three decades.

Georgia and North carolina

Democratic Strength in the South

Nowhere is the Senate picture brighter for Democrats than in the South, where two popular and well-known Democrats have raced out to leads in states Mr. Trump carried two years ago.

In Georgia, Senator Jon Ossoff, a Democrat and the youngest sitting senator, has a huge war chest and consistently leads his Republican rival, Representative Mike Collins, in the polls. His advantage, which Georgia Republicans attribute in part to his focus on constituent services, has led some Republicans to write off the race, and some Democrats to encourage him to run for president in 2028.

In neighboring North Carolina, the Democratic nominee, former Gov. Roy Cooper, is trying to flip a seat and is running as a tough-on-crime moderate. He has never lost an election. Mr. Cooper consistently leads his Republican opponent, Michael Whatley, in the polls, with some showing him ahead by double digits.

Matt Zdun contributed reporting.