J. Joe Ricketts, the founder of TD Ameritrade, helped finance an anti-Trump super PAC in the GOP primaries. (AP)

TD Ameritrade founder J. Joe Ricketts intends to give at least $1 million to a super PAC supporting Republican presidential candidate Donald Trump, a dramatic reversal from the GOP primaries, when he and his wife were top financial backers of an effort to prevent the real estate developer's nomination.

Ricketts's expected contribution, first reported by the Wall Street Journal and confirmed by a person familiar with his plans, could signal a rush of new money for the Republican nominee.

Ricketts's support for Trump, which could come in form of a donation to a group opposed to Democratic contender Hillary Clinton, comes amid signs that billionaires Sheldon and Miriam Adelson are finally pouring money into pro-GOP groups. The Adelsons may give to organizations run by Ricketts, and the two families are expected to closely coordinate their strategies.

Ricketts's decision to jump into the presidential is particularly startling, considering that Trump threatened to expose secrets about his family, which owns the Chicago Cubs. After Ricketts's wife, Marlene, gave an initial $3 million to the anti-Trump group Our Principles PAC, Trump tweeted that the Ricketts family "better be careful, they have a lot to hide!"

In all, Marlene and Joe Ricketts contributed $5.5 million to Our Principles PAC, which ran a slew of hard-hitting ads against Trump. It remains to be seen where they will direct their money for the general election.

Correction: An original version of this post erroneously called the Ricketts family a member of the #NeverTrump movement. While they opposed his candidacy in the primaries, after he secured the nomination, they stopped financing efforts against him.