A Florida-based super PAC that made more than $1 million in contributions in 2010, almost all of it underwritten by the former CEO of online brokerage TD Ameritrade, is emerging as a factor in Tuesday's Republican Senate primary in Nebraska.

In the three days before the election, the Ending Spending Action Fund has dumped almost $255,000 into the race to help Deb Fischer, a state senator who has suddenly turned an already-heated contest for the GOP Senate nomination into a three-way race. The group has not yet disclosed any donors this year, but in the 2010 campaign cycle, $1.16 million of the slightly more than $1.18 million raised by ending spending came from broker-turned-philanthropist J. Joe Ricketts.

Ricketts, who retired as head of TD Ameritrade in 2008 and left the board of directors in 2011, is a prolific political giver who had donated $500,000 to another one of this year's most active super PACs, the Campaign for Primary Accountability. Sunlight's Influence Explorer shows that he also has given to the presidential campaigns of just about anyone who was running for the GOP presidential nomination this year: Mitt Romney, Jon Huntsman, Rick Perry, Rick Santorum, Tim Pawlenty, Newt Gingrich, Michele Bachmann, Ron Paul, and Gary Johnson.

The Nebraska Senate race has attracted more than $2.4 million in outside spending, Sunlight's Follow the Unlimited Money tracker shows, with much of it focused on the contest between Attorney General Jon Bruning, the favorite of the party establishment, and state Treasurer Don Stenberg, who has the backing of various tea party-affiliated groups. 

But with a week to go before the election, conservative rock star Sarah Palin weighed in on Fischer's behalf. The first expenditures by Ending Spending came days after her endorsement. The winner of the GOP primary will face former Sen. Bob Kerrey, who is attempting a comeback to keep the seat in Democratic hands when incumbent Sen. Ben Nelson, D-Neb., retires at the end of the year.

Ending Spending's Nebraska ad buys appear to be the super PAC's first federal spending of the 2012 campaign cycle. The group's website features an ad for Wisconsin Gov. Scott Walker, the target of a recall election this year. Two years ago, Ending Spending targeted Senate Majority Leader Harry Reid, D-Nev., and Reps. John Spratt, D-S.C., Chet Edwards, D-Texas, and Walt Minnick, D-Idaho. All but Reid lost. 

On its registration forms with the FEC, the super PAC lists the same address as that of the Robert Watkins accounting firm. Watkins is listed as the PAC's assistant treasurer; his wife, Nancy, is the treasurer. 

Late last year, the Occupy Tampa movement staged a demonstration outside the Watkins firm's Tampa headquarters against the multiple super PACs that protestors said the company is operating. Sunlight's call to the Watkins office for comment on the super PAC's spending in the Nebraska race, was not returned.