Ameritrade executive Peter Ricketts was poised Thursday to enter the 2006 Republican Senate race after resigning his post at the online brokerage firm.

Ricketts announced he would leave his company position effective Aug. 26 to "explore an opportunity in public service."

Although he was not available to elaborate on his plans, Ricketts has privately informed a number of Republican officials he intends to seek the Senate seat held by Democratic Sen. Ben Nelson.

Already in the GOP derby are former Attorney General Don Stenberg and former Republican State Chairman David Kramer.

Ricketts, 40, resigned as chief operating officer of Ameritrade Holding Corporation, but will continue to serve as vice chairman of Ameritrade's board of directors.

Ameritrade's success has "motivated (me) to evaluate how I might leverage my corporate world experience in public service," Ricketts said in a statement released by the company late Thursday afternoon.

Ricketts was responsible for Ameritrade's retail client business as well as clearing and marketing operations.

Ricketts would not be available for further comment, said Donna Kush, director of corporate communications.

Stenberg and Kramer welcomed him into the race.

"If Pete decides to get in, it ultimately would make me a stronger candidate in the general election," Kramer said by cell phone as he drove back to Omaha from campaign stops in Hastings.

"I think having three folks like Pete and Don and myself would demonstrate the vulnerability of Ben Nelson."

Stenberg said Ricketts' entry would make the contest "look more and more like the 2000 Republican Senate primary."

In that contest, he said, he defeated "two candidates who each spent about a million dollars of their own money."

Stenberg sailed to victory over George Grogan and Elliott Rustad in the 2000 primary, in addition to Scott Moore, David Hergert and John DeCamp. But Nelson defeated him in the general election.

Republican State Chairman Mark Quandahl said he expects Ricketts to announce his plans in the near future.

If Ricketts enters the Senate race, Quandahl said, that "would enhance and sharpen the competition."

And that, he said, would be "good news for us as we make sure the person who emerges from the primary as the Republican nominee will be in the best position to beat Ben Nelson."

David DiMartino, Nelson's spokesman in Washington, said he had no comment on speculation Ricketts would enter the race.

Ricketts was active last year in the successful campaign to defeat efforts to broaden gambling options in the state.

Although there was no clear indication of any connection with Ricketts' decision, President Bush's White House political advisor, Karl Rove, spoke at Ameritrade last month.  The site was chosen by the Nebraska Republican Party, not by the White House.

Reach Don Walton at 473-7248 or at dwalton@journalstar.com.