With the stakes high and next month's primary election rapidly approaching, Nebraska's Republican Senate candidates aren't playing touch football anymore.

One day after Shane Osborn's Senate campaign launched an attack ad directed at Ben Sasse, supporters of Sasse responded Wednesday with an ad targeting Osborn.

The "Ensuring a Conservative Nebraska" political action committee ad stated that Osborn's campaign is "funded by Washington lobbyists who support Obamacare" and said a 2009 state audit found that Osborn "engaged in unreasonable and unnecessary spending" when he was state treasurer.

A day earlier, the Osborn ad described Sasse as a candidate funded by special interests and "beholden to Washington."

On Wednesday, the Osborn campaign noted that the auditor report cited in the anti-Osborn ad involved the rejection of about $1,300 in expenses for two officewide working lunch meetings of the state treasurer's staff in 2009.

The lunch meetings at Lazlo's in Lincoln incurred a $679 cost in May and $671 in September. 

The Osborn campaign said the political action committee sponsoring the new ad is funded by a Fremont donor who has ties to Sasse, the current president of Midland University in Fremont.

Meanwhile, Osborn announced that he will participate in a Nebraska telephone town hall session with Grover Norquist, president of Americans for Tax Reform, on Thursday evening.

Omaha banker Sid Dinsdale and Omaha attorney Bart McLeay round out the Republican Senate primary foursome.

Reach the writer at 402-473-7248 or dwalton@journalstar.com. On Twitter @LJSDon.