Three liberal justices won another 10-year term on the Pennsylvania supreme court, giving Democrats a key victory and allowing them to maintain their 5-2 advantage on a vital body that could issue important rulings on abortion and voting rights in an important battleground state in the coming years.

In Pennsylvania, supreme court justices are first elected in partisan elections and then voters get to decide whether to retain them every 10 years in contests that are technically non-partisan. Three justices – Christine Donohue, Kevin Dougherty and David Wecht – were elected as Democrats in 2015.

The court since then has played a major role in election disputes, striking down the state’s severely gerrymandered map in 2018 and ruling in favor of Pennsylvania voters in disputes about mail-in ballot rules.

Only one justice has not been retained in Pennsylvania since 1968. If Donohue, Dougherty, and Wecht had all been ousted, it could have led to a 2-2 court, with judges from other courts potentially rotating in, because a special election would not have taken place until 2027. The Pennsylvania governor Josh Shapiro could make interim appointments to fill the vacancies, but would have been extremely unlikely to get the necessary two-thirds support in the state senate.

Judicial retention contests are typically low-turnout contests, but this year’s race in Pennsylvania saw an influx of attention and campaign cash. Spending in the race was set to exceed $15m, according to the Associated Press. In recent years, there has been a wider recognition on the immense power state supreme courts have to shape state policies and consequently more spending on their elections. Campaigns and outside groups spent more than $100m in a state supreme court election in Wisconsin earlier this year.

Since state supreme courts often decide matters of election law, there is an intense focus on their composition in swing states such as Pennsylvania, Wisconsin and North Carolina.

Underscoring the importance of the contest, Donald Trump weighed in during the final days of the election and urged voters to vote against retention, calling Donohue, Dougherty and Wecht “radical supreme court justices”. Barack Obama urged voters to support retaining the justices, as did Shapiro and Ken Martin, the chair of the Democratic National Committee, who campaigned in the state ahead of the election.