The Republican establishment stayed silent through much of this election cycle, and then suddenly, they weren't silent anymore.

Now, they talk of nothing but stopping Republican presidential candidate Donald Trump from clinching the nomination - a mad scramble which could have been avoided if they had been able to coalesce around one candidate earlier, said experts.

"The Republican party elite was very divided. In most cases, during the period we call the invisible primary, before people start voting, they rally around somebody. They didn't do that this time," said Associate Professor David Karol, from the department of government and politics at the University of Maryland.

He added that with more conservative elements supporting Texas Senator Ted Cruz, and more moderate factions supporting the likes of former Florida governor Jeb Bush, "it gave an opening for Trump".

Elected party officials, party employees, interest groups and supporters from major industries are often regarded as part of the party establishment, which has a stake in the winner's policies.

More generally, "these are people who are involved in elections over a period of time and want something out of politics - they desire certain policies," said associate professor of political science Marty Cohen from James Madison University.

"They don't just want to win elections, they want to win elections and gain policy from that," said Dr Cohen.

This is why Mr Trump is not the establishment pick.

"Donald Trump is a loose cannon," said Dr Cohen. "They want someone who is sort of a guarantee that if they do win, they are going to be a positive force for what the party wants."

For example, while the party establishment is generally pro-free trade, Mr Trump has been championing protectionist policies, speaking of slapping tariffs on imports from China and Mexico.

Over the last few weeks, former Republican presidential nominee Mitt Romney has become the face of the "Never Trump" movement, asking voters to vote for anyone but Mr Trump in order to prevent the property mogul from picking up the 1,237 delegates needed for the nomination. Millions of dollars have also been spent on attack advertisements against Mr Trump.

But "right now the power of the establishment to stop Mr Trump seems minimal," said Iowa State University's department chair for political science Mack Shelley.

At the convention, delegates are not bound to a candidate after the first ballot, so if Mr Trump does not get a majority during the first ballot, then "anything goes".

The rules can even be changed to "hand the nomination to someone else if they (the establishment) so choose and can get coordinated on one particular alternative," said Dr Cohen.

At the moment, Mr Cruz trails Mr Trump in the primaries, but he is regarded as less than ideal too.

"The problem is that Cruz is also a very polarising figure and a lot of people really don't want him... Trump versus Cruz is a terrible choice," said Dr Karol.

Apart from Mr Cruz, Speaker of the House Paul Ryan "possibly could be recruited for the role, but is reluctant to do so after going through a very similar process to become Speaker of the House. Other white knight possibilities do not seem to be very likely to have the gravitas to be taken very seriously", said Dr Shelley.

Mr Trump himself has warned that if he remains the Republican front-runner but is denied the nomination, there would be riots.

So at this point, while the establishment may have the power to choose a nominee, they hardly stand to gain, no matter what they do.

"They can end up with Trump, whom they don't really like or trust; they can block him, then they are going to provoke a very big reaction... theoretically, it is possible, but it is hard to see them nominate anyone other than Cruz whom they don't like either," said Dr Karol.

"Hillary Clinton couldn't have asked for a better scenario."

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