(CNN) - A GOP strategist working on behalf of Rep. Mike Castle in Delaware's GOP primary for Senate said he wishes robo-calls against Tea Party favorite and Castle opponent Christine O'Donnell had been made earlier, according to CNN senior political analyst Gloria Borger.
The robo-calls, released by the state GOP, allege that O'Donnell was living off her campaign donations and failed to pay staffers. O'Donnell has denied the allegations.
Some establishment Republicans have said they believe Castle has a better chance of winning the general election, which would let the GOP pick up a seat currently held by Democrats and possibly help Republicans take control of the Senate.
Borger said she asked a GOP strategist working on Castle's behalf what he would do differently in this race.
"You know, I would have run those robo-calls earlier against Christine O'Donnell," Borger said she was told by the strategist, who she did not name.
"So, it shows you how tense this is and how tough this is, because Republicans are not fooling around here. They want to win back control of the Senate, and Republicans in Washington are saying, 'She's not going to do it for us,' " Borger said.
In the robo-call - calling likely Republican voters and released by the state Republican party - a woman identifying herself as O'Donnell's campaign manager for her 2008 Senate bid accuses O'Donnell of "living on campaign donations" and alleges O'Donnell "just wanted to make a buck" and "is no conservative." O'Donnell's campaign has denied she misappropriated campaign funds in 2008.