ATLANTA (AP) — Trying to defend their narrow Senate majority with a challenging slate of contests on Republican-leaning turf, Democrats are pumping $25 million into expanded voter outreach across 10 states.

The new spending from the Democratic Senatorial Campaign Committee, first shared with The Associated Press, comes less than two months until the Nov. 5 election and as Democrats are benefiting from a fundraising surge since President Joe Biden ended his reelection bid in July and endorsed Vice President Kamala Harris as the party standard-bearer.

"A formidable ground game makes all the difference in close races," DSCC Chairman Sen. Gary Peters of Michigan said in a statement. "We are reaching every voter we need to win."

The latest investment will be distributed across Arizona, Florida, Maryland, Michigan, Montana, Nevada, Ohio, Pennsylvania, Texas and Wisconsin. The money will go toward efforts to defend five Democratic incumbents and open seats in Michigan, Maryland and Arizona that are currently included in Democrats' majority, as well as efforts to unseat GOP incumbents in Florida and Texas.

Plans for the money will vary by state but will include hiring more paid field organizers and canvassers; digital organizing programs targeting specific groups of voters online; texting programs; and in-person organizing events targeting younger generations and nonwhite voters.

Democrats currently hold a 51-49 Senate advantage, a split that includes independent senators who caucus with Democrats. But of the 33 regular Senate elections this November, Democrats must defend 23 seats, counting the independents who caucus with them to make their majority. They've devoted few national resources to West Virginia, a Republican-leaning state where Sen. Joe Manchin, a Democrat-turned-independent, is retiring.

The playing field gives Democrats little margin for error. If they lose West Virginia and hold all other seats, they still would have to upset Florida Sen. Rick Scott or Texas Sen. Ted Cruz to win a majority or hope Harris wins the presidential election — an outcome that would allow her running mate, Tim Walz, to cast the tiebreaking vote for Democrats as vice president, as Harris did in a 50-50 Senate during the first two years of Biden's administration.

The DSCC declined to disclose a state-by-state distribution of the $25 million. But it's no secret that Democrats' defense of the majority starts with tough reelection contests for Sens. Jon Tester of Montana and Sherrod Brown of Ohio. Both are relatively popular, multiterm incumbents, but they're running in states where Donald Trump, the former president and current Republican nominee, has twice won by comfortable margins. That means Tester and Brown would need a considerable number of voters to split their tickets between Trump and their Senate choice.

Senate Democrats already have financed field offices in Montana and Ohio, since those are not presidential battleground states where the Harris campaign leads Democrats' coordinated campaign operations. And even with the money coming from national coffers, the additional on-the-ground spending will reinforce the two Democratic senators' strategies of distancing themselves from Harris and the national party.

Five of the 10 states getting money, meanwhile, overlap with the presidential battleground map: Arizona, Michigan, Nevada, Pennsylvania and Wisconsin. Biden won all of them four years ago, while Trump won all except Nevada in 2016. Both presidential campaigns see the states as tossups this fall.

The voter outreach spending comes alongside an ongoing $79 million advertising effort by Democrats' Senate campaign arm and builds on staffing and infrastructure investments that the national party arm already has made.

The outlay comes after Harris, who has raised more than $500 million since taking over the Democratic presidential ticket in July, announced plans to distribute $25 million to party committees that focus on down-ballot races. Senate and House Democrats' respective campaigns each got $10 million of that money, an acknowledgment that Democratic majorities on Capitol Hill would make a Harris presidency more successful and that Harris and down-ballot Democrats can help each other at the ballot box.

Democratic aides said the on-the-ground spending was always in the Senate committee's plans, but Harris' bounty certainly expands options for all party-affiliated campaign groups. Democrats believe they have a superior campaign infrastructure to Trump and the rest of the GOP in a campaign year where the White House and control of Capitol Hill could be decided by marginal turnout changes among the parties' core supporters and a narrow band of persuadable voters.

Still, the National Republican Senatorial Committee has outraised and outspent Senate Democrats this cycle, though Democrats had more cash on hand at the end of July, the last reporting period disclosed to the Federal Election Committee.

Through July 31, the NRSC had raised $181.3 million and spent $138.5 million. Republicans reported a balance of $51 million. Democrats had raised $154 million and spent $103.3 million. They reported a balance of $59.3 million.