The bruising Delaware GOP primary battle between Rep. Mike Castle and Tea Party Express-backed Christine O'Donnell just got a little nastier with a new robocall going statewide Tuesday morning.

The new call, obtained by Fox News' Trish Turner,  features O'Donnell's former campaign manager in 2008, Kristin Murray, who slams her former boss. You can listen to the call here

Murray says, "I got into politics because I believe in conservative values and wanted to make a difference. But I was shocked to learn that O'Donnell is no conservative."

Other campaign staffers have also recently come out with negative statements about their former boss. O'Donnell has admitted to making financial mistakes, and critics have charged she violated campaign finance laws.

Murray said she left the campaign because, "As O'Donnell's manager, I found out she was living on campaign donations - using them for rent and personal expenses, while leaving her workers unpaid and piling up thousands in debt. She wasn't concerned about conservative causes. O'Donnell just wanted to make a buck."

O'Donnell in recent weeks has made a surprise surge in the GOP race to fill Vice President Biden's former Senate seat, and has served as a narrative for the 2010 midterms, with all eyes seeing how well Tea Party-backed candidates do. The outcome of this primary is seen by many as a bellwether for how establishment GOP candidates fair against the Tea Party groups, who have less money and organization.

(Find out more about how turnout is on the ground from Fox New's exclusive newsletter Power Play, part of the new AEHQ iPhone app)

Castle, a moderate Republican also served two terms as governor and is the longest serving congressman in Delaware history. The winner of Tuesday's Republican primary will face off Democrat Chris Coons.

Fox News' Trish Turner contributed to this report.