One of the pet issues the Conservatives like to bring up when they want to needle the Liberals is outstanding debt on the part of contenders in the last Liberal leadership race. I guess we're supposed to assume that there are no Conservatives in similar situations but that assumption would be incorrect.
... [Conservatives are] curiously mum about 80 candidates - including 21 Conservatives - who are similarly in arrears on money borrowed to fight the 2004, 2008 and 2011 election campaigns.
Did not know that. I can understand why opposition parties might be reluctant to draw a lot of attention to the issue when some of their own are among those in arrears.
Notice that it doesn't stop the Harper Conservatives.