Former President Donald Trump has $102 million in political cash he can wield as the GOP eyes retaking majorities in Congress next year, according to filings made Saturday night with the Federal Election Commission.

Mr. Trump’s political-action committees reported receiving $82 million during the first half of the year through June 30, with $62 million of that flowing to Save America PAC, a leadership committee that issues Mr. Trump’s press statements and candidate endorsements.

Some of that money came in the form of transfers of donations raised last year, the filings show, a caveat first reported by the New York Times and not mentioned in a statement released by Save America PAC announcing the figure.

Trump aides didn’t immediately respond to a question about the accounting.

It is early in the midterm election cycle and committees often wait to give to candidates until closer to the start of voting. Mr. Trump’s committees, which can donate $5,000 per election to a campaign, reported no donations to GOP campaigns through June 30.

The fundraising figures show that even after losing the 2020 election and being banned from multiple social-media platforms, Mr. Trump remains a draw for donations from Republican voters, particularly through email and text-message solicitations.

He has asserted his leadership over the party by summoning candidates for endorsements and repeatedly teasing a possible presidential campaign in 2024, holding back a crop of would-be candidates that includes prominent senators and former Trump administration members. Democrats have thin advantages in the Senate and House.

Mr. Trump was particularly successful on the Republican donation platform WinRed. The platform’s public filing Friday showed Mr. Trump’s committees raised more than $56 million in online donations—more than any other GOP group on the platform during the first half of the year.

Some of that went to the Republican National Committee as part of a joint fundraising agreement with the Trump Make America Great Again committee. But the majority went to committees controlled by Mr. Trump—Save America PAC, his joint fundraising committees and MAGA PAC, his former campaign that has been converted into a multicandidate committee.

Mr. Trump’s biggest online fundraising day, according to the WinRed filing, was on Feb. 28 when he gave a speech before the Conservative Political Action Conference and made a special appeal for his supporters to give directly to his committees. His second-biggest online fundraising day was Jan. 5, the day before he delivered a speech outside the White House challenging the election results, with his supporters later rioting at the Capitol.

In a statement Saturday night, Mr. Trump said he “can’t imagine a more important time to elect good Republicans to the House and Senate. Commonsense conservatives were never more badly needed.”

Yet even as the former president has handed out more than two dozen endorsements for state, local and congressional candidates, his committees haven't followed them up with campaign contributions.

Rep. Julia Letlow (R., La.), who Mr. Trump endorsed and who won a special election in March, didn’t receive a campaign contribution. And at least through July 7, the latest date for which data is available, neither did Susan Wright, a Trump-endorsed candidate who lost the runoff election to a fellow Republican last week in Texas’ Sixth Congressional District.

Instead, Trump’s political-action committees have spent on lawyers, fundraising, events, staff and consultants, many of whom were involved in the former president’s campaign. Committees controlled by Mr. Trump also reported spending nearly $290,000 at his properties and businesses for various expenses.

In mid-June, Save America PAC gave $1 million to America First Policy Institute, a nonprofit launched by former Trump administration officials earlier this year. Among those involved in the institute is Chad Wolf, the former acting secretary of Homeland Security, and John Zadrozny, who served in the Trump White House.

Parscale Strategy, a firm owned by former Trump campaign manager Brad Parscale, was paid more than $52,000 for digital consulting and some consulting related to Mr. Trump’s recount efforts.

The filings also detail the winding down of the Trump campaign and the transition of that committee into its current form as Make America Great Again PAC.

Overall, that committee paid out nearly $8 million in legal fees during the first half of the year—about $4.7 million connected to consulting on the 2020 campaign, $2.1 million related to recount efforts and a little less than $1 million more involving recent legal consulting for the PAC, the filings show.

The most legal fees—$2.5 million—went to Kasowitz, Benson & Torres LLP, the law firm of longtime Trump lawyer Marc Kasowitz.

Jones Day, an international law firm with a large presence in Washington, and Harder LLP, the law firm of media-law specialist Charles Harder, both were paid more than $500,000.

The PAC also paid Elections LLC, a firm founded by former deputy campaign manager Justin Clark and former White House lawyer Stefan Passantino, $200,000, its filing shows.

The same firm earned a little more than $51,000 from Save America PAC and another $40,000 for legal consulting from the PAC’s affiliated joint fundraising committee.

Write to Chad Day at Chad.Day@wsj.com and Alex Leary at alex.leary@wsj.com