Fredreka Schouten

USA TODAY

WASHINGTON — Democratic presidential candidate Hillary Clinton and her allies neared the $1 billion mark in fundraising as her party’s donors helped the first female major-party nominee build an enormous financial advantage for the campaign’s final weeks.

Clinton and the fundraising committees she operates with the Democratic National Committee collected more than $773 million through the end of September, and Clinton’s leading super PAC announced Thursday that it had raised nearly $155.4 million over the course of the election cycle.

That makes Priorities USA Action the best-funded super PAC of the 2016 campaign to date. September’s haul marked its strongest performance of the election as the group raised in $24.6 million in four weeks.

Clinton and her joint fundraising committee started October with about $152 million in cash reserves that can help fund advertising and get-out-the-vote operations in key battlegrounds, her campaign said Thursday night. Her Republican rival, Donald Trump, and his aligned groups had half that.

“Our donors understand what’s at stake in this election,” Priorities spokesman Justin Barasky said in an email. “It really is a choice between the most qualified person to ever run for president and the most divisive and dangerous man to be nominated by a major party in modern history.”

Tom Steyer, a billionaire environmentalist who has raised money for Clinton and has poured millions into his own political organizations to bring out voters before Election Day, said the “momentum is very good if you’re a Democrat.”

“The question is: How much of a historic election will we have?”

Tom Steyer ups the ante to turn out Millennials

Both candidates stepped up their campaign activity last month, spending more than they raised.

Clinton spent $82.6 million, up from $49.6 million the previous month, according to her filing Thursday night with the Federal Election Commission. Trump's campaign increased spending to $70.2 million last month, up from $29.9 million in August. Its biggest vendor: Giles-Parscale, the Texas firm that its handles digital consulting and online advertising. It received $20.6 million last month.

A smaller expense also drew attention: Trump made a final $100,000 severance payment last month to his former campaign manager and current CNN contributor Corey Lewandowski. In all, Lewandowski's firm, Green Monster Consulting, received more than $500,000 during the life of the campaign.

Small donors and Trump himself fueled the campaign. Slightly more than $56 million came from the candidate's personal fortune, still well short of the $100 million Trump told supporters at his rallies that he would spend.

Trump has used his vast social media following to attract online contributions. About 64% of contributions to Donald J. Trump for President during the election cycle have came from donors who gave $200 or less. By comparison, 25% of Clinton's donors gave in amounts that small.

Wednesday, Trump 's campaign tapped his legions of followers to raise $9 million during two Facebook Live events it staged to look like news programs during the final debate with Clinton. More than 150,000 people donated during the live-stream, which featured interviews with Trump surrogates, such as former New York City mayor Rudy Giuliani.

Trump began active fundraising in late May, and the Democrats’ massive financial advantage emboldened Clinton and her allies to train their firepower on traditionally Republican states, such as Georgia and Arizona, in an effort to broaden the political map and deal Trump a humiliating defeat on Election Day.

This week, Clinton’s campaign announced an expanded advertising campaign in Arizona, a red state where first lady Michelle Obama stumped for Clinton at a rally Thursday in Phoenix to encourage early voting.

Two other Clinton allies, Vermont Sen. Bernie Sanders and daughter Chelsea Clinton, visited the state this week.

Priorities, flush with cash and increasingly confident of a Clinton win, is expanding its advertising effort to the Senate, where Democrats need a net gain of just four seats to take control from Republicans.

Its first Senate ad, released Thursday, attacks Sen. Kelly Ayotte, R-N.H., for failing to condemn Trump for his incendiary rhetoric during much of the campaign. Ayotte, a freshman senator, disavowed the New York businessman this month after a tape of him talking about groping women became public.

A second ad targets Sen. Pat Toomey, R-Pa., and seeks to tether him to Trump's controversial comments about abortion.

Priorities said it started October with $22 million available in the bank.A single donor, financier Donald Sussman, donated more than $6 million to Priorities last month. Facebook co-founder Dustin Moskovitz gave $2.5 million

The group announced its fundraising totals as the presidential candidates and many super PACs prepared to file reports with the Federal Election Commission Thursday detailing their fundraising and spending in September.

Contributing: Christopher Schnaars