To flip-flop to make yourself look good for Southern Social Conservatives.
To run for senate Governor in Massachusetts supporting Gay Rights and Pro-Choice values, then switching your position when you run for President.
To Take credit for Social Programs that you did not support and in some cases vetoed. Taking credit for balancing the Massachusetts state budget while claiming that you are not a big spender.
To interfere with the States veiws to look good national
"Don't vote of a Mitt Romney Flip-Flopper" you'll never know what he supports.