I’d say the number one factor is the Liberal belief that Republicans are selfish, uncaring capitalists who don’t mind seeing people starve. Republicans tend to ignore that accusation and don't typically demonstrate compassion or caring.
Republicans differ from Liberals because their moral point of view is different. Not better or worse, just different. Liberals look at welfare as essential to protect disadvantaged groups, and don’t worry about the cost to deliver the services they need. Republicans worry about value and effort. They are willing to support the disadvantaged if the programs designed to help them are efficient and don't waste money.