Millions of Americans are about to decide the future of the Republican-controlled Congress in a midterm election that will have a significant impact on President Donald Trump's final two years in office.

All eyes are on a handful of Senate races that will decide control of the prized upper chamber.

A four-seat gain by Democrats would give them control – and with it the power to limit Trump's ambitions, reject his judicial nominations and investigate his administration.

Billions of dollars are being poured into the 35 races across the country, but only a handful could go either way.

There are seven Senate races deemed to be a toss-up by independent elections analyst Cook Political Report, external.

Here, we profile the personalities making waves in these much-watched contests.

In a nutshell:

This race has been marred by controversy over the appearance of a second candidate named Dan Sullivan on the ballot. The Republican senator of that name faces stiff competition from Mary Peltola and accuses her of introducing his namesake to confuse voters, which she denies.

Story of the race:

The race may ultimately be the tipping point state that decides which party controls the chamber if, as expected, Alaska is one of the slower states to reach an outcome.

Peltola, a former House member and the first Alaska Native to be elected to Congress, has run on a platform of "fish, family, freedom" and has attacked Sullivan's record as Alaska's natural resources commissioner.

Two-term senator Sullivan, a long-time Marine Corps reservist who also served as Alaska's attorney general, has accused Peltola's campaign of links to an effort to confuse Republican voters which led to a second man named Dan Sullivan entering the race.

The Peltola campaign denies any such link, though the issue is the subject of a state investigation and a justice department lawsuit, which on Sunday was rejected by a judge.

Alaska's ranked-choice system also adds uncertainty to the mix, and the state has historically been difficult to poll, with surveys historically underestimating Republican voters.

How they got here:

Sullivan, 61, only retired from the US Marines as recently as 2024, after a 30-year career that included deployments in to Afghanistan and the Middle East. Peltola, 53, grew up fishing salmon with her father, later becoming the first person born in the state to actually represent it in Congress.

In a nutshell:

One of the few Republican senators who voted to convict Trump when he was impeached in 2021, Susan Collins has consistently outperformed her party in this Democratic-leaning state, partly by presenting herself as a rebel. Her opponent Troy Jackson, who draws on his background as a lumberjack to persuade blue-collar Mainers he can relate to them, hopes that time is finally running out for one of the survivors of US politics.

Story of the race:

Collins is hoping her reputation as a centrist will persuade independent-minded voters in a state that reliably votes Democratic in presidential elections.

Now her campaign will test whether Republicans can win by distancing themselves from Trump.

Collins, who is seeking her sixth term, entered the midterm cycle as one of the most vulnerable incumbent Republicans seeking re-election.

But she has been helped by controversy on the other side of the aisle involving Graham Platner, who was ultimately replaced as the Democratic nominee by Jackson, a former president of the Maine state senate.

Both Jackson and Collins oppose Trump's tariffs on Canada, mindful of the impact they are having on this border state. Unlike Collins, though, he favours the abolition of the US Immigration and Customs Enforcement agency (ICE).

How they got here:

Collins, 73, began her political career fresh from college in the 1970s and she entered the US Senate in 1997. Jackson, 58, is a logger who became politically active when he helped to lead a protest to block lower-paid workers from Canada entering Maine.

In a nutshell:

James Talarico aims to end a decades-long electoral drought for the Democrats in Texas – and show that one of the Republicans' main strongholds could be in play for the 2028 presidential election. His match-up with Ken Paxton has become the most expensive Senate race ever.

Story of the race:

Republican Paxton knows his party has been winning statewide races in Texas for more than 30 years.

Texas State Representative James Talarico, a former schoolteacher and Presbyterian seminary student, is the latest Democrat hoping to break his party's long losing streak.

Texas Republicans are facing a daunting combination of headwinds. It is a challenging national political environment for conservatives and there are several state issues like data centre construction and aggressive immigration enforcement that have cut against their party. Added to that is a controversial candidate, Paxton.

The campaign has been acrimonious, with Talarico targeting Paxton's 2023 impeachment by the Republican-controlled state House of Representatives for alleged corruption, bribery and abuse of power. Paxton denied the charges and was later acquitted by the state Senate, calling the impeachment a "politically motivated sham from the beginning".

Supported by more than $170m in funds from tech mogul Elon Musk, Paxton has attempted to paint Talarico as a liberal who is out of touch with Texans on issues like transgender rights, law enforcement, immigration and energy policy.

A Democratic victory here might indicate America's second-biggest electoral prize in a presidential election could be within their reach in 2028 – a notion that could dramatically reshape the nation's political landscape.

How they got here:

Before he entered public service, Paxton spent 14 years launching and building his own law firm. He served in the state House and Senate before becoming the chief legal officer in Texas.

Talarico taught at a middle school in San Antonio, in a neighbourhood he has described as one of the poorest in the state. He has studied theology and names Pope Leo as a "spiritual hero".

In a nutshell:

This is one of the most bitter contests, with left-wing candidate Abdul El-Sayed aiming to keep this crucial seat in Democratic hands. He is up against Mike Rogers, a Republican former FBI agent who received a surprise endorsement from El-Sayed's defeated Democratic rival, only adding to the acrimony that has characterised this race from the start.

Story of the race:

A doctor and public health official, El-Sayed is one of the most left-wing Senate nominees this election cycle.

He supports a government-run health insurance system and the abolition of ICE. His strong criticism of Israel has been a source of tension in the party.

Rogers, who emphasises his military and intelligence background, has managed to maintain Trump's support despite decrying his Canada tariffs and his Russia diesel deal.

He has also diverged from the president by calling for a quick end to the war with Iran. El-Sayed would be the first Muslim person ever elected to the US Senate.

As well as attacking him for his politics, Trump and Rogers have sought to link him to the Muslim Brotherhood; El-Sayed has denounced the organisation.

The president has also invoked 9/11 and even called him a "jihadist" without citing any evidence, prompting a backlash and accusations of Islamophobia.

How they got here:

El-Sayed, 41, was born and raised in Michigan before his medical studies in the US and UK and subsequent work in the sector. Rogers, 63, served in the US Army and in the FBI before entering Congress and emerging as a key advocate of US surveillance policies.

In a nutshell:

Trump made the trip to Iowa on his final day of campaign rallies, such is its importance. Polls have it as a toss-up between Republican and former TV news host Ashley Hinson and Democrat Josh Turek, who won gold at basketball at two Paralympic Games.

Story of the race:

Farms, tariffs and Trump have all emerged as key issues in the closely-watched race.

Hinson has slightly distanced herself from the president, urging him to end the war with Iran and breaking with him on easing beef tariffs, while at the same time defending Trump's broader tariff policies as important.

Meanwhile, Turek argues that Trump's tariffs have led to "farmageddon" in the largely rural state. He has also sought to convince voters that the war in Iran has led to rising fuel and fertiliser costs.

Hinson has cast Turek as a candidate who would vote as an "East Coast liberal".

The two have also clashed on issues ranging from taxes and social security to immigration. The last time a Democrat won a federal election in Iowa was nearly 20 years ago.

How they got here:

Hinson, 43, is a former local news reporter who says her journalistic background helps her understand the issues faced by the state's farmers and small businesses. Turek, 47, was born with spina bifida, going through multiple surgeries before representing the USA at wheelchair basketball at four Paralympic Games, twice triumphantly.

In a nutshell:

A Democratic victory in Kansas would upend 94 years of history – the last time this Midwestern state elected a Democratic senator was 1932. Senator Roger Marshall is the Republican trying to avoid a humbling defeat, while first-time candidate and Methodist pastor Adam Hamilton is the Democrat trying to break records.

Story of the race:

Marshall has closely aligned himself as a Trump-aligned, pro-farmer candidate.

Hamilton, who once considered running as an independent, has pitched himself as a candidate that can bridge the partisan divide. He has largely campaigned on a message of lower costs and protecting healthcare access.

Marshall has sought to attack Hamilton's record as a pastor, describing him as "too woke" for the conservative state.

Marshall, meanwhile, has been under scrutiny ever since reports emerged that he sued patients unable to pay their medical bills. He told Fox News the story was a hit job by the left media and senior Democrats.

The tight race is broadly seen as a potentially ominous sign for Republicans.

A Hamilton victory would be seen as a sign of increasing dissatisfaction with Trump's policies – particularly on economics – in territory that was once considered safe for the party.

How they got here:

Both Marshall, 66, and Hamilton, 62, highlight that they are fifth-generation Kansans who are in close touch with local issues. Marshall worked for 25 years as an obstetrician, delivering some 5,000 babies, while his rival Hamilton founded a church which became the centre of the largest United Methodist congregation in America.

In a nutshell:

Trump won this state with ease in 2024 and no-one a year ago considered it in play for the midterms. But Republican Senator Jon Husted finds himself neck and neck with Democrat Sherrod Brown who is running to get his old job back, having represented Ohio in the Senate for many years before losing his seat.

Story of the race:

Husted was appointed in 2025 to the Senate seat vacated by Vice-President JD Vance, and is now running to serve the rest of Vance's term.

He promises to use his business experience to bring jobs and growth to Ohio.

In a different election cycle he would probably be the favourite to win this onetime swing state that has become reliably red in the Trump era.

But Husted is facing a formidable challenge from Brown, who has high name recognition from three decades representing Ohio in Congress.

Brown is known as a champion of workers and was advocating economic populist policies long before others in his party.

The race is a referendum on Trump's economic policies, in particular his trade wars that have impacted the manufacturing and auto industries that underpin Ohio's economy.

How they got here:

Husted, 59, began life in a foster home and was in the world of business before politics; he was an elite American football player at college and his physique has been repeatedly praised by President Trump at rallies. Brown, 73, was introduced to political activism from a young age and was recruited into local politics even before graduating from Yale.

By Bernd Debusmann, Daniel Bush and Anthony Zurcher in Washington, and James FitzGerald and Tom Geoghegan in London.