US Senate elections: the key races that will determine power in Washington

Ashley Kirk, Tom McCarthy and Helena Robertson

While the world’s attention is on Donald Trump’s attempt to win re-election as president over challenger Joe Biden, the battle for the US Senate that will culminate on 3 November is equally dramatic.

Even if Biden defeats Trump, he will be unable to pass legislation on key issues such as healthcare, immigration and climate change unless the Democrats simultaneously seize the Senate, where the Republicans now have a 47-53 majority.

A map of Senate seats up for election

The Democrats could pull it off. Democratic challengers in two states, Arizona and Colorado, appear to have a good chance in defeating Republican incumbents, while only one Democratic incumbent, in Alabama, looks especially vulnerable, according to the latest forecast from the Cook Political Report.

The number of additional seats the Democrats need to win for a voting majority depends on who wins the White House, since any Senate tie of 50-50 is broken by the sitting vice-president. If Trump wins re-election, the Democrats probably need three states, in addition to Arizona and Colorado, for the majority; if Biden wins, the Democrats probably need only two more.

“Probably” because there is enough time for races not mentioned here to shift and change the calculus.

A forecast of the balance of power in the Senate

Where will those seats come from? There are seven races currently judged as tossups by the Cook Political Report’s Senate forecasts.

Top Democratic targets: the seven tossups

The Democrats’ top targets are Maine, North Carolina and Iowa.

In all three races, incumbent Republicans appear to be weighed down by the unpopularity of Trump, while their Democratic opponents could benefit from high turnout among voters who wish to see Trump defeated.

A history of Senate tossups

Broad demographic trends are also making trouble for Republicans nationally, with fewer women saying they will support Trump in 2020, suburban voters likewise abandoning him, according to the polls, and support for Trump falling off even among whites without a college degree.

In Maine, the longtime Republican incumbent Susan Collins appears at last to have fallen out with the electorate, a majority of whom say they disapprove of Collins’ vote to confirm Brett Kavanaugh, Trump’s second pick to join the supreme court.

In North Carolina, the Republican incumbent, Thom Tillis, has defended Trump’s handling of the coronavirus crisis, while a majority of voters say they supported the state’s Democratic governor in his clash with Trump over public health rules for hosting the Republican national convention.

While the Republican Joni Ernst had looked difficult to beat earlier this election cycle, she also appears to have suffered from defending Trump’s pandemic policies, and challenger Theresa Greenfield has shown unexpected strength.

But with the campaign still ongoing, these and other races still have time to change.

Republicans are hoping that the political fight over the supreme court nominee Amy Coney Barrett will galvanize conservative voters, just as the fight over Kavanaugh did in the 2018 midterm elections. And last-minute political fallout from the debates, the Covid crisis, the economy or some unforeseen twist could change the races yet again.