Despite his recent claims about how he could just leave it all behind, Brown plotted and schemed to get power for years and won't give it up. He'd rather see his party destroyed at the next election than admit he's in any way to blame for their failures.
BTW, is it just me or does Cameron's new girl on the block* look and sound like a 'B' grade clone of Ruth Kelly?**
*
http://news.bbc.co.uk/1/hi/uk_politics/8166769.stm
**
http://news.bbc.co.uk/1/hi/uk_politics/4100061.stm