Pragmatism is a straightforward practical way of thinking about things or dealing with problems, concerned with results rather than with theories and principles. It was created by American Progressives as a method which rejected philosophical principles. It measures ideas not bases upon whether they are right or wrong, but by how practical they are. Politicians are often described as pragmatic if they change their policies, or even their professed beliefs, based on what will produce results in a given political climate, or what will win them votes.
Pragmatism is also a philosophical school with origins in the United States which postulates that truth is whatever is useful and rejects foundationalism. Perhaps the most well-known pragmatist was William James, who wrote extensively on the subject of religious experience and was writer Henry James' brother. The late philosopher Richard Rorty is also remembered as a "neo-pragmatist". Hu Shi, a famed Chinese modern thinker who was prominent in the pre-Communist China was also influenced by American pragmatism. It rejects the notion of absolute right and wrong, good and evil, and ultimately defines truth as that which is useful, meaningful, helpful. Ideas that don't seem workable or relevant are rejected as false. 
Pragmatism is a form of nihilism since it rejects philosophical principles, it is also similar to moral relativism. As Ben Shaprio stated "Human beings have moral duty not out of pragmatism but out of principle."  Liberals often use pragmatism to advocate for ideas based not on morals or principles but on what is more practical. Such as cheating may be perceived as a more practical way to pass a class, or win a game, despite it being wrong. Pragmatism also leads to the opposition of Conservative ideas, for instance, President Ronald Reagan called for the war on drugs, which may liberals oppose on the basis on what is practical rather than morals and principles. The opposite of pragmatism is idealism.
Pragmatism also causes mediocrity. As Greatness, being the antithesis of mediocrity, comes from daring to think great thoughts and take great risks, however being realistic prevents this. This raises the question and thought of "What would Thomas Edison or Nicola Tesla invented if they had decided to be realistic instead of pursuing their dream? The same applies to Rockefeller, Morgan, or Getty? Where would they be if they had been realistic?"  This all hinders innovation, as the people who make real differences in this world are not focused on the odds, or coming up with endless reasons why something can’t work.