Why has the GOP become, the "Party of No"? the "Coalition of the Unwilling?" the "Contras?" Because it is a coalition of widely diverse interests that have little in common except "no."
The GOP can be roughly divided into 3 large groups.
(1) fiscal conservatives, laissez-faire economists who want less government and more free markets;
(2) social conservatives who want to outlaw abortion, outlaw gay marriage, abstinence only sex education, and prayer and religion in schools;
(3) military hawks, who want a strong military.
The problem with this coalition is that they have very little in common with each other. Military hawks want more spending and bigger government. To a large extent, social conservatives also want more government interference in schools and in restricting reproductive choice and marital choice. Real fiscal conservatives want a smaller military, and less government subsidies to schools.
Essentially the only thing they have in common is "no", and the vague Rorschach slogan of lower taxes. Everyone liberals and conservatives believe a large portion of our taxes is wasted on things they don't support, whether it's failing schools or failing prisons, AFDC or a bloated military.
They agree to disagree about everything.