NEW YORK (Reuters) - A super PAC supporting Robert F. Kennedy Jr's presidential campaign received $5 million in April from Timothy Mellon, the latest donation the 81-year-old banking heir has made to the independent candidate, according to a monthly filing released on Monday.

The donation from Mellon, who has been a key backer of Republican candidate Donald Trump in recent years, to the Kennedy-supporting American Values 2024 comes after already giving at least $20 million to the Kennedy super PAC.

American Values 2024 ended April with $20.85 million cash on hand, according to the filing with the Federal Election Commission, after spending to get Kennedy on state ballots and other expenses.

Mellon, a scion of the Pittsburgh-based Mellon banking family, has given the pro-Trump super PAC known as MAGA Inc at least $16.5 million since 2022. During the 2020 presidential election, Mellon gave at least $20 million to another pro-Trump super PAC, America First Action Inc.

Efforts by Reuters to contact Mellon for comment through a publisher were unsuccessful.

Kennedy would draw about 13% of national votes in a three-way matchup with Democratic President Joe Biden and Trump, a recent Reuters/Ipsos poll shows. It's unclear whether he'd draw more from Democrats or Republicans; Reuters interviews show his fans include former supporters of both Democratic President Joe Biden and Trump.

Mellon's contributions to the RFK super PAC, which can receive donations of unlimited size but cannot coordinate with campaigns directly, are an effort to siphon away votes from Biden and help Trump, the Democratic Party claims.

"MAGA Republicans are hellbent on propping up RFK Jr to be a spoiler for Trump in this race," said Matt Corridoni, spokesperson for the Democratic National Committee (DNC).

American Values 2024 disputed that contention.

"The RNC (Republican National Committee) also says Bobby Kennedy is a spoiler," said Tony Lyons, co-chair of American Values 2024. "If RFK Jr can burst through the tricks, the scare tactics, the censorship and the lies, the DNC and the RNC know that he can win."

Trump has also taken aim at Kennedy. On his social media platform Truth Social, Trump in April called Kennedy "a Democrat 'Plant'" and "a Radical Left Liberal."

Kennedy's candidacy has also been bankrolled by his vice presidential pick Nicole Shanahan, a wealthy tech lawyer from California. She gave Kennedy's campaign about $8 million in April, according to the most recent campaign filing. In March she gave $2 million to the campaign.

Shanahan, the former wife of Google co-founder Sergey Brin, previously also gave $4 million to American Values 2024.

(Reporting by Stephanie Kelly; Editing by Heather Timmons and Leslie Adler)

By Stephanie Kelly