In the latest jab in the Republican race for lieutenant governor, Lt. Gov. David Dewhurst is formally asking opponent Sen. Dan Patrick to release his tax returns. “Dan Patrick has refused to release his tax returns despite numerous requests from the press, as well as public challenges from Todd Staples and Jerry Patterson in the primary,” the campaign said Tuesday.

The request is the latest in a string of attacks on Patrick’s financial past. Last week, Dewhurst came out swinging with a new TV ad, highlighting Patrick’s failed business dealings and bankruptcy filing back in the 1980s. Patrick walked away from about $800,000 in debt after a chain of sports bars he co-owned failed.

Tuesday, Dewhurst campaign spokesman Ryan Hecker said,

“After admitting to pocketing his employees payroll tax withholding and leaving a string of unpaid creditors chasing after assets held in a dizzying number of financial entities, voters are beginning to see the truth about Dan Patrick. David Dewhurst has released full tax returns from 2009-2012, and he is calling on Dan Patrick to provide the same transparency.”

Patrick has defended his financial past, saying he’s never tried to cover up his hardships. “I learned from that. It made me the fiscal conservative that I am because I am 63 today, I was 35 then,” he said in an online interview.