Two groups on the left with differing missions are joining forces to bolster their preferred candidates in state supreme court races in November, as such elections grow increasingly expensive and politically polarizing.

The two organizations — the National Democratic Redistricting Committee, the Democrats’ arm in fighting for state and congressional maps; and Planned Parenthood Votes, the political arm of the abortion health care organization — will initially target races in Arizona, Michigan, Montana, North Carolina, Ohio and Texas. The fund, with a budget of $5 million, will provide digital ads along with funding for canvassing and get-out-the-vote operations.

“Our aim is to protect the independence of state supreme courts, to ensure that they are composed of justices who are dedicated to interpreting the law in a neutral way, who will adhere to precedent and who will protect the fundamental rights of all citizens,” Eric H. Holder Jr., the former attorney general who is chairman of the redistricting group, said in a statement announcing the joint venture.

Until recent years, state supreme court races were traditionally relatively nonpartisan affairs — in most states candidates are not officially affiliated with a political party — though partisan leanings could be gleaned from judicial rulings. But political interest in state supreme court races has exploded, culminating in a $50 million race for State Supreme Court in Wisconsin last year.

National interest in state government battles has rapidly accelerated since Donald J. Trump was elected president in 2016. State-level races, including ones for governor, secretary of state and legislatures, were estimated to surpass $7 billion in fund-raising in 2022. And with Congress largely deadlocked, heated political and policy debates have largely unfolded at the state level.

Many groups, both Republican and Democratic, will pour money into state supreme court races this year. The Republican State Leadership Committee spent more than $4.3 million on state supreme court races in 2018, and it has not announced plans for 2024.

The alliance between the redistricting organization and Planned Parenthood was forged over four years, when the United States Supreme Court issued landmark rulings upending both the governance of redistricting and abortion access.

In 2019, the Supreme Court ruled in Rucho v. Common Cause that federal courts are powerless to hear challenges to partisan gerrymandering, leaving state courts the lone venue to fight against a political tilt to a district.

And last year, the Supreme Court left abortion access up to the states, and state supreme courts have played an increasingly critical role in finalizing laws regarding abortion. Just last month, it was the State Supreme Court in Arizona, and not its Legislature, that restored an 1864 law that effectively banned abortion in the state. (The Republican-led Legislature would later repeal that ban.)

“We are in the fight of our lives to protect and restore our fundamental freedoms,” Alexis McGill Johnson, president of the Planned Parenthood Action Fund, said in a statement. “And our courts are the front lines.”