Nebraska Attorney General Jon Bruning said Monday that he had raised $721,200 by the end of June to prepare for a possible campaign against incumbent U.S. Sen. Chuck Hagel.

Bruning’s campaign said more than 80 percent of those donations came from Nebraskans, including a few prominent donors like legendary Nebraska football coach Tom Osborne and billionaire Walter Scott, retired CEO of Omaha construction giant Peter Kiewit Sons’ Inc.

“Raising the money needed to challenge an incumbent is very difficult,” Bruning said.

The Republican attorney general says he has raised more money at this stage of the campaign that any of the three Republican candidates for U.S. Senate did in 2005.

In their initial 2005 filings, Pete Ricketts reported raising $372,621.69; David Kramer reported raising $171,920; and Don Stenberg reported raising $33,102.34. Ricketts won the Republican nomination and went on to lose to Democratic U.S. Sen. Ben Nelson last November.

Bruning’s campaign released preliminary fundraising figures on Monday even though his quarterly report to the Federal Election Commission isn’t due until July 16.

Bruning didn’t officially join the Senate race until early last month, but he has been preparing to run for higher office for some time. For instance, Bruning ran unopposed for re-election last fall, but still ran campaign ads designed to build name recognition statewide.

No other candidates have officially joined the Senate race but several people have said they are considering running.

Hagel has said that he will make an announcement about his political future later this year.

Hagel’s political director, Kevin Chapman, said Monday the campaign won’t report its fundraising figures until the deadline, “but we’ll be well beyond $700,000.”

Federal Election Commission reports show that Hagel had $230,214 on hand at the end of March.