Ameritrade chairman and founder Joe Ricketts talks to shareholders in Omaha, Neb. on Feb. 16, 2005. (Dave Weaver/AP)

First it was Sheldon Adelson, a casino mogul who helped finance Newt Gingrich’s presidential ambitions. Then it was Foster Friess, a multimillionaire with the propensity for off-color jokes who threw his money behind Rick Santorum.

The latest wealthy businessman to grab headlines in this year’s presidential contest is someone less splashy, who made a splash on Thursday nonetheless: Joe Ricketts, the low-key founder of Omaha-based TD Ameritrade, emerged in connection with a plan to blitz the airwaves with provocative attacks on President Obama.

A billionaire philanthropist with a particular interest in opposing earmarks, Ricketts had previously played a bit part on the political scene. But he took an unflattering turn in the spotlight Thursday with a New York Times article that said a report he commissioned detailed how his super PAC, Ending Spending, could put $10 million toward an ad campaign about Obama and the Rev. Jeremiah A. Wright Jr., his controversial former pastor.

Ricketts and his family, which owns the Chicago Cubs and includes in its ranks a high-profile Obama fundraiser, moved quickly Thursday to disavow the racially charged idea.

“Not only was this plan merely a proposal — one of several submitted to the Ending Spending Action Fund by third-party vendors — but it reflects an approach to politics that Mr. Ricketts rejects, and it was never a plan to be accepted but only a suggestion for a direction to take,” Brian Baker, president of the fund, said in a statement.

The dust-up highlights a danger for presidential campaigns in the era of super PACs, which have made it easier for wealthy individuals and corporations to spend freely on campaigns. Although the candidates may reap the benefits of that spending, they also face the risk that the groups or their donors will go rogue, pursuing lines of attack that reflect on them negatively.

Romney was forced repeatedly Thursday to comment on the proposal — overseen by GOP ad man Fred Davis — which derided Obama as a “metrosexual, black Abe Lincoln.”

“I want to make it very clear: I repudiate that effort,” Romney told reporters in Florida. “I think it’s the wrong course for a PAC or a campaign. I hope that our campaigns can respectively be about the future and about issues and about vision for America.”

Liberals seized on the incident, with the group Americans United for Change calling for a boycott of Ameritrade “until they publicly call on Ricketts to shut down his hate-spewing super PAC.”

The incident highlighted the relatively private Ricketts, 70, who has recently increased his participation in conservative politics and is poised to play a significant role in the 2012 election.

Ricketts has an unusual profile for a rising political player, with little in his résuméto suggest that he favors controversial or attention-getting tactics.

A former Democrat who became a Republican, he later renounced all party affiliation to become an independent. His daughter, Laura, is a lesbian activist and prominent bundler for Obama; she raised about half a million dollars for the president.

“We have different political views on how to achieve what is best for the future of America, but we agree that each of us is entitled to our own views and our right to voice those views,” Laura Ricketts said in a statement today. “Above all we love and respect each other.”

Ricketts’s children have roles with the Cubs, which is seeking help from Chicago Mayor Rahm Emanuel (D) to renovate the team’s 98-year-old stadium, Wrigley Field. Emanuel, Obama’s former chief of staff, is “livid” with the Ricketts family, an aide to the mayor said.

According to a 2006 Omaha World-Herald profile of one son, Pete Ricketts, who ran unsuccessfully for U.S. Senate, Joe Ricketts wouldn’t allow any of his children to work for Ameritrade before their 30th birthday, wanting them to expand their horizons before returning to the family business.

The family’s net worth has been ranked as high as 93rd on the Forbes 400 list of the wealthiest Americans. In 2009, Joe Ricketts ranked 371st, with assets estimated at $1 billion.

According to friends, Ricketts has rarely sought the spotlight or spoken publicly. He left the Ameritrade board of directors in February but gave little indication that he intended to become more involved in politics.

“I don’t think he seeks to be the public face of anything like that, but I would say the things that he believes in, he’s very passionate about,” said Robert Slezak, a former Ameritrade executive who worked with Ricketts for a decade. “I think he would prefer to deflect the spotlight on someone else.”

Yet Ricketts has been an emerging financial force in politics in recent years, initially by starting an anti-earmark campaign called Taxpayers Against Earmarks. He donated $1.1 million to Ending Spending ahead of the 2010 midterm elections, with the bulk spent opposing Senate Majority Leader Harry M. Reid (D-Nev.).

This month, Ricketts helped guide Nebraska state Sen. Deb Fischer to an upset victory in the GOP Senate primary with a late $250,000 infusion. Ending Spending also is supporting Wisconsin Gov. Scott Walker (R) in his recall election next month.

And Ricketts is a top donor this year to the Campaign for Primary Accountability, a group that has targeted long-time incumbents regardless of their party affiliation or politics.

“He has a lot of different interests, and he’s at a point in his life where he can spend his time and money on things that interest him and are important to him, and that includes the political world around him,” said Mark Quandahl, a friend and former chairman of the Nebraska Republican Party.

Ricketts owns a successful new New York news Web site,; a natural bison meat producer; and the upstart American Film Company, which produced the 2010 Robert Redford movie “The Conspirator,” a historical documentary about the legal aftermath of Abraham Lincoln’s assassination.

Staff writers T.W. Farnam, Dan Balz, Dan Eggen and Nia-Malika Henderson contributed to this report. Henderson reported from Jacksonville, Fla.