That sound you hear is the noise made by the Republican Party establishment crashing and burning.  The only remaining question for them is how far they will go to blow up what remains?

The GOP, as it has been known for decades, is no more.  The cadres of white, upper-crust, east-coast establishmentarians has been elbowed aside by the upstarts Donald Trump and Ted Cruz.  And nothing they can do from here on out will change that.

They have no viable candidate.  They have no agenda to speak of.  Their rationale for being has been smashed.  All they have left is to play a spoiler role by attempting to deny Donald Trump the nomination.

In this, they will fail.  The rules they wrote in 2012 to prevent an outsider like Trump from gaining power will now be turned against them.  There is no convention challenge that will prevent Trump from giving his nomination acceptance speech as long as he has the 1237 delegates needed to win the nomination. And his Super Tuesday performance virtually guaranteed that scenario. 

Bereft of any hope of stopping Trump, that won't prevent the GOP establishment from spending tens of millions of dollars anyway.

Politico:

With every victory, Trump is splintering the party, evoking strong emotions from an increasingly outspoken group of detractors and from the rank-and-file voters propelling his candidacy and rendering the GOP’s Washington power brokers powerless.

“We have expanded the Republican Party,” Trump said Tuesday night, noting the spike in turnout across this year’s GOP primaries. “I am a unifier. I know people will find it hard to believe, but I’m a unifier.”

“The Republican Party has become more dynamic, more diverse,” he continued. “We’re taking from the Democrats, we’re taking from the independents. We have a lot more people.”

As usual, Trump’s words contained more than a grain of indisputable truth. But it’s his other words—the schoolyard insults and crude New York City vernacular that masks a lack of knowledge about policy, the xenophobic dog whistles so loud they sound like a bark, the attacks on Republican elders, moderation on Planned Parenthood, even neutrality in the Israel-Palestine conflict—that so many Republicans cannot abide. As they dig in against his candidacy, they are girding for a civil war not, they insist, in order to cling to power over the party but to save the ideas and principles that have always held it together.

It is a war the GOP as we know it may not survive, “a big and strong fight going on about the future of the Republican Party as intense as we’ve ever seen,” said Pete Wehner, a veteran of the George W. Bush White House who has savaged Trump of late. “A Trump victory would be catastrophic to the Republican Party and a terrible danger to the republic itself. If he wins the presidency, you may see the efforts to form a new party.”

The disconnect between the Republican establishment and its donor class and the party’s grassroots base has been widening for years, ever since Barack Obama took office in 2009. But the increasing likelihood of Trump becoming the GOP standard-bearer is tearing whatever fraying threads had held this fractious coalition together.

As Trump racks up wins, his party is splitting into two factions with immeasurable distance between them—the #NeverTrump crowd on one side and the Make America Great Again movement on the other.

The Republican Party is a huge entity, much bigger than any one man or one faction.  So the chances are pretty good that there will continue to be an organization that calls themselves "Republicans."

But the question being asked by some in the establishment is valid; what does this new GOP stand for?  Trump, and Cruz to some extent, have been all about blowing up the party, breaking from the past, ignoring longstanding GOP positions on vital issues.  In short, Trump has no clue what his campaign stands for.  Whether by design or by simple ignorance, Trump will be the Republican Party standard-bearer not because he stands for anything specific, but because he has promised to change things.

If what's left of the GOP establishment carries through with their threats to upend the Trump campaign, it will be a massacre in November regardless of who the Democratic Party nominee might be.