By the mid-1940s, there was a split between liberals and conservatives in the democratic party focusing on

 The contentious issues had to do with the New deal and issues to do with human rights.  The new deal which was a signature policy of Roosevelt, and which had helped alleviate the great depression suffering was increasingly facing criticism from the conservatives who believed it was a great toll on big companies. Issues to do with civil rights for the blacks were also highly divisive.