What would be so bad if the RNC called Trump's bluff and stopped backing him?

In what way is the RNC currently "backing" Trump?

"why not say 'go'?"

They might be treating him well in the hopes that he'll lose the nomination, but not run as an independent.

"If he stays in and wins the Republican nomination, the Republicans lose"

Not necessarily.

I guess you don't understand how our political parties work. If he wins the primaries and is nominated at the convention, they do not have any choice but to support him. That is how our system works.

It isn't like a European political party which can expel a member for failing to toe the party line. And that is why we have only two viable parties, instead of dozens of them which make coalitions and hold new elections when a vote of no-confidence is taken. .

If they renege on the deal with Trump....he could go Independent, get maybe

15% of the R votes....guaranteeing a win for the Dem candidate.

UPDATE: I think the Trump Circus act will destroy a deeply-flawed Hillary on the campaign trail.

Well, right now the man has a majority of the voter base. They didn't want him to go Independent because they knew he would split the base and they would lose. If they stopped backing him, they would lose a majority of their voting base and they would lose.

They aren't going to win the White House anyway, and at least they can regain their dignity.

The RNC is not backing him.

They had to support him if he gets the nomination..They all signed the pledge.

Huh?

They would only hurt themselves.