Voters in the United States are heading to the polls on 6 November, and the choices they make could have big implications for science.

Here are some of the races and ballot measures that Nature is watching. We'll be updating our story tonight as election results roll in.

Washington state carbon-tax proposal

Washington could become the first US state to tax carbon emissions if voters there approve a ballot measure called Initiative 1631. It would impose a US$15-per-ton fee on carbon in 2020, raising the price by $2 annually until 2035. The money raised by the tax — predicted to reach more than $1 billion per year by 2025 — would be used for government programmes on air and water quality, energy and forest health.

A poll in early October suggested that 50% of voters backed the tax proposal, while 36% opposed it. But a similar ballot measure failed to pass in 2016, and oil companies have spent tens of millions of dollars campaigning against Initiative 1631.

Space races

Representative John Culberson (Republican, Texas) is a space enthusiast who heads the House spending panel that oversees NASA, the National Science Foundation and the National Oceanic and Atmospheric Administration. But this year his stalwart support for a NASA mission to Jupiter's moon Europa , whose icy surface is thought to conceal a vast ocean with the potential to harbour alien life, may cost him politically.

Culberson's opponent, Democrat Lizzie Fletcher, has accused him of favouring pet projects such as the Europa mission and neglecting local issues in his district near Houston — such as the severe floods caused by Hurricane Harvey in 2017. The latest polls show Culberson and Fletcher running neck-and-neck.

Also facing a tough re-election bid this year: Senator Bill Nelson — a Florida Democrat, former NASA astronaut and the top-ranking Democrat on the Senate Commerce, Science and Transportation Committee. Nelson has criticized his Republican opponent, Florida Governor Rick Scott, over his response to the toxic "red tide" algal bloom that has plagued Florida's Gulf Coast for months.

Scientists on the ballot

Roughly 50 candidates with backgrounds in science, technology, engineering or medicine ran for the US House of Representatives this year; fewer than half made it past the primaries to the general election. Here are some who are still in the race.

• Arizona: Emergency-room physician Hiral Tipirneni, a Democrat, is trying to unseat Representative Debbie Lesko, a Republican.

• Illinois: Lauren Underwood, a registered nurse and former senior adviser to the US Department of Health and Human Services during the administration of President Barack Obama, is running for the House as a Democrat. Her opponent is Representative Randy Hultgren, a Republican who sits on the House science committee.

• Michigan: Physician Matt Longjohn is challenging Representative Fred Upton, a Republican — and climate sceptic — who holds a prominent position in the House Energy & Commerce Committee.

• Pennsylvania: Chrissy Houlahan, who holds degrees in engineering and has worked as a business executive and head of a literacy group, is running for an open seat.

• Texas: Joseph Kopser, a technology entrepreneur with a degree in aerospace engineering, is competing for the House seat being vacated by Republican Lamar Smith, the controversial head of the House's science committee .

Efforts to stop gerrymandering

Three states will vote on proposals to address gerrymandering, the act of drawing voting districts to favour one party over another. Ballot measures in Colorado, Michigan and Utah would establish independent commissions to draw electoral boundaries, rather than leaving the task to politicians. In recent years, mathematicians have joined the fight against gerrymandering , developing computer models and algorithms to reveal bias in electoral maps — and to propose how to redraw them with fairer boundaries.