Ambac Financial hits record low after bigger-than-expected quarterly loss

** Shares of property and casualty insurer Ambac Financial AMBC.N plunge as much as 28.3%; hitting their record low

** Stock last down 20.4% at $6.65

** AMBC late Monday reported bigger-than-expected Q1 loss, missing Wall Street expectations for the third straight quarter, according to data compiled by LSEG

** Roth Capital Partners says estimating earnings for AMBC remains challenging, given all the changes over the past year in its business

** Brokerage believes AMBC earnings can improve fairly quickly, as the company grows in the insurance distribution business

** Both brokerages covering the stock rate "buy" or higher; with a median PT of $15 - LSEG

** As of last close, AMBC stock down 34% YTD