WASHINGTON — Planned Parenthood’s political arm is targeting eight states with competitive Senate and governor’s races in its largest-ever midterm election campaign.

The offensive is set to cost $20 million, an initial mark that the organization’s officials say is all but certain to be exceeded.

The investment from Planned Parenthood Action Fund and Planned Parenthood Votes, the organization’s political entities, makes it one of the biggest outside spending forces in Democratic politics headed into a cycle in which the party sees a rare opportunity to pick off GOP seats across the map.

It’s part of Planned Parenthood’s effort to sustain the momentum of the Women’s March the day after President Donald Trump’s inauguration and turn women’s health care and reproductive rights into issues that drive voters to the ballot box to oppose Trump and GOP candidates.

The initial list of targets includes eight states: Arizona, Florida, Michigan, Minnesota, Nevada, Ohio, Pennsylvania and Wisconsin.

It comes on top of $4.5 million spent on last year’s governor’s races in Virginia and New Jersey.

The groups are set to announce their plans later Thursday.

The targeted states are part of a two-for-one approach of prioritizing states with competitive races this fall for both Senate seats that could help Democrats keep Trump in check and governors’ offices that are crucial to the redistricting process after the 2020 Census.

“This is our last chance to flip some of those governors’ seats before redistricting,” said Deirdre Schifeling, the executive director of Planned Parenthood Votes. “A lot of those states have governors who have been terrible for women, terrible for access to reproductive health care.”

Arizona and Nevada are particularly important: The states represent Democrats’ two best chances of picking off GOP-held Senate seats this cycle, with Nevada Sen. Dean Heller seen as vulnerable in a state Hillary Clinton won and Arizona Sen. Jeff Flake retiring in what’s rapidly becoming a swing state.

A handful of House races are likely to join the list of targets, with officials eyeing contests in California, New Jersey, New York and Texas as potential targets. And state legislative races and attorneys general contests are also on a watch list of races that could be added.

Planned Parenthood is also spending money in Democratic primaries, including backing Marie Newman in her bid to unseat Illinois Rep. Dan Lipinski, who opposes abortion rights.

Planned Parenthood’s political arms argue that reproductive health has been a driving issue in recent elections, citing the group’s own polling showing that black voters moved toward Ralph Northam in the Virginia governor’s race by 19 points and older voters and moderates also moved in Northam’s favor after hearing reproductive health care and rights messaging. In Nevada, the group argues, Republican former Rep. Joe Heck’s opposition to Planned Parenthood was a deciding factor in Democratic Sen. Catherine Cortez Masto’s win in 2016.

The emphasis of the digital program, in a nod to the reshaped electorates in Virginia and Alabama’s Senate special election, is on engaging with infrequent voters, young people and people of color, especially women. It will begin with efforts to engage with those voters on issues they care about and persuade them that their voices matter in the current political moment and later switch to a focus on elections and individual candidates. The organization is also planning large-scale, state-level training programs for activists.

“We’re doing this work in such a way to make sure that we are furthering this activism we’re seeing in this moment into long-term electoral engagement,” Robinson said.

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