Conservative religious leaders are struggling to mobilize a broad, coordinated effort to get evangelicals to the polls in November as some donors balk at supporting Donald Trump.

An alliance of more than 70 groups is targeting about 24 million registered voters across eleven battleground states who have identified themselves as born-again Christians and didn't cast a ballot in the 2012 election, according to United in Purpose, the group coordinating the effort. The lists include millions of people in states that President Barack Obama won by narrow margins.

Yet, with fewer than three months to go before the Nov. 8 election, many key donors are either withholding funds altogether or insisting their money goes only to support House and Senate candidates, not Trump's bid for the White House.

"We're seeing a lot of folks that say I want to give to a state like North Carolina or efforts in certain parts of Florida or certain parts of Nevada," said Timothy Head, executive director of the Faith and Freedom Coalition. "They're avoiding a Trump investment and targeting it toward a particular Senate race."

Trump, though, is counting heavily on evangelical support in November.

He has far less support from that base than Republican nominee Mitt Romney did in 2012, according to a recent poll by NBC and the Wall Street Journal.

Unlike Clinton's campaign, Trump has spent little so far on his ground game, mostly relying on the Republican National Committee for its get-out-the-vote operations. Social conservative groups, such as the United in Purpose, are a crucial complement to the RNC's work because they can reach a different set of people: those who don't regularly vote but care about specific issues like abortion and same-sex marriage.

"More of the burden is going to shift to advocacy groups because they don't have a really solid infrastructure in the campaign," Tony Perkins, president of the Family Research Council, said.

Clinton's campaign, on the other hand, has invested heavily in field offices and voter mobilization. At the same time, labor unions, environmental organizations and other groups are also working to turn out their members.

Mobilizing Trump voters could cost evangelical groups millions, depending on which states are in play after Labor Day, when the voter outreach is supposed hit full speed. Head estimates his group will need to spend up to $10 million — about three times as much as it did in the 2014 mid-term elections.

Head's Faith and Freedom Coalition is aiming to make more than 200 million distinct contacts with potential voters using direct mail, email, social media, 800 paid canvassers and several thousand volunteers manning phone banks.

The funding gap "does make us have to prepare contingencies instead of going full blast," Head said. "But I have a lot of confidence that we're going to end up with all the resources we need."

Among the donors withholding support are billionaire industrialists Charles and David Koch, who have been outspoken in their opposition to Trump. The Koch's group Freedom Partners Chamber of Commerce supported evangelical get-out-the-vote efforts in 2012 and 2014, according to its disclosures with the Internal Revenue Service, contributing more than $1 million to Family Policy Alliance, the political arm of Focus on the Family, and $230,000 to American Values Action, a group run by Gary Bauer, a Reagan administration official who served as head of the Family Research Council.

"The Koch Brothers obviously have not been able to reconcile themselves on Trump so they're concentrating their resources on Senate and House races," Bauer said. That could leave Trump without an extensive evangelical battlegrounds without Senate contests, like Virginia and Michigan. "We just have to wait and see how the presidential races and the Senate and House races interact with each other."

As the group's struggle to bring in money, the Trump campaign's fundraising has recently stepped up. Trump raised $80 million for his campaign and other party entities in July, the campaign said.

In the primaries, leaders of many social conservative groups chose to endorse Texas Sen. Ted Cruz after holding a series of meetings with all of the candidates. Trump, who wasn't even among the finalists, did well with evangelical voters nonetheless. Part of his appeal, Perkins said, was an oft-repeated line in his campaign speeches, that Americans would start saying "Merry Christmas" again.

"Even I was kind of caught off guard by the simplicity but the profound nature of the subtle messaging," said Perkins, who had endorsed Cruz in the primaries. Trump "was communicating something very profound, that we're going to protect freedom of religion, but it pretty much evaded the radar."

Trump has gone beyond subtle messaging since securing the nomination. He promised to appoint pro-life judges to the Supreme Court in a June meeting with Christian conservatives. Trump has promised on the campaign trail to end federal funding for Planned Parenthood, and has promised to reverse a the provision in the tax code, pushed by then-Senator Lyndon Johnson in 1954, that prevents pastors from endorsing candidates from the pulpit.

"He's the first person in modern American politics to even broach the subject to taking on the so-called Johnson amendment," Head noted. "Pastors across the country get really, really excited about that."

There are signs, though, that evangelicals still aren't convinced by Trump. In a survey published in July, the American Culture and Faith Institute, which polls and analyzes trends among conservative Christians and churches, found that 62 percent of their pastors intended to encourage their congregants to vote, down from 78 percent in the 2014 mid-terms.

"There are some key pastors who will be engaged, there are some who won't," said Bill Dallas, chief executive officer of United in Purpose.

In addition to churches, United in Purpose is partnering with groups including the Family Research Council, Faith and Freedom Coalition, Concerned Women of America, 60 Plus Coalition, Tea Party Express and Bound4LIFE, an anti-abortion group. The groups are targeting Colorado, Florida, Iowa, Michigan, Ohio, New Hampshire, Nevada, North Carolina, Pennsylvania, Virginia and Wisconsin. Nine of the states also have contested Senate races.

United in Purpose identifies potential voters by comparing its partners' mailing lists to voter rolls to find people who haven't been voting. They have established goals in terms of the number of voters they're hoping to reach in each state: more than 473,000 in Florida; 354,000 in Ohio and 263,000 in Virginia. Those numbers far exceed Obama's 2012 statewide margin of victory.

George Barna, executive director of the American Culture and Faith Institute and a longtime analyst of the views and voting habits of Christians, said the Democrats might be doing the same thing.

"The great unknown, of course, is the extent to which organizations attempting to do similar work among liberals will be successful in their efforts," Barna said.