That cracking, thudding sound emanating from Indiana on primary night Tuesday was the crumbling of a Washington institution, punctuated by muffled shrieks of terror from incumbent office-holders everywhere.

Republican Sen. Richard Lugar—a towering figure in the national-security, arms-control, and foreign-policy realms who six years ago was so popular in his home state that local Democrats didn’t bother to field an opponent—lost his bid for a seventh term to a lesser-known, more modestly financed challenger who successfully portrayed the 80-year-old incumbent as out of touch and not conservative enough.

In 2006, Lugar won reelection with 87 percent of the vote. Tuesday night, as the returns rolled in, the Senate’s longest-serving Republican was losing in a humiliating landslide to Indiana State Treasurer Richard Mourdock—the candidate supported by Indiana’s disparate Tea Party groups and bankrolled by Washington’s socially conservative and free-market, tax-hating business lobbies.

As if to confirm the Tea Partiers’ suspicions about Lugar, his Democratic colleague on the Senate Foreign Relations Committee, Chairman John Kerry, called his defeat a “tragedy for the Senate.” And President Obama called Lugar “a friend and a colleague” while expressing his “deep appreciation for Dick Lugar’s distinguished service in the U.S. Senate.”

Lugar went down swinging, issuing a less than magnanimous concession statement that will give aid and comfort to Rep. Joe Donnelly, Murdock’s Democratic opponent in the general election. “If Mr. Mourdock is elected, I want him to be a good Senator,” Lugar’s statement said. “But that will require him to revise his stated goal of bringing more partisanship to Washington. He and I share many positions, but his embrace of an unrelenting partisan mindset is irreconcilable with my philosophy of governance and my experience of what brings results for Hoosiers in the Senate. In effect, what he has promised in this campaign is reflexive votes for a rejectionist orthodoxy and rigid opposition to the actions and proposals of the other party.”

Mourdock and his backers spent more than $2.7 million to defeat Lugar, who, along with his allies, forked over $3.3 million to lose badly—but his campaign still had $1.4 million in the bank as of April 18. Mourdock’s 22-point victory clearly came as a shock.

“I’m a little bit sad that he would be beaten, and disappointed,” said former Wyoming senator Alan Simpson, who two months ago had predicted to The Daily Beast that his old friend Dick Lugar would somehow survive the primary. “He was—is—one of the most brilliant, savvy, articulate guys, and he could do all this stuff without notes.”

Simpson attributed his friend’s downfall to, among other factors, “voter fatigue.”

Former Republican congressman Mark Souder of Indiana said Mourdock assured his victory two weeks ago during a televised debate with Lugar, in which he was articulate, knowledgeable, and even ventured into Lugar’s wheelhouse, foreign policy, without making a mistake. A poll released Friday, in which Mourdock was 10 points ahead, indicated that the debate was an inflection point in the race, with 30 percent of those surveyed moving to an unfavorable opinion of the 36-year incumbent.

What’s more, Lugar—who hasn’t faced a tough opponent since 1976—was clearly rusty at the business of campaigning, making avoidable mistakes such as allowing his lack of Indiana residency to become an issue, bringing in Condoleezza Rice (not a favorite among Republican primary voters) to spend two days campaigning for him, and as recently as this past weekend, stressing his role in negotiating arms-control agreements with the Russians—not a compelling issue in recession-damaged Indiana.

“On Monday, they took Lugar to a senior center to play darts. He’s 80. What are you thinking?” Souder marveled. Worse still, the white-haired Lugar missed the dart board entirely at least twice, once launching a dart to the floor and another time almost hitting a cameraman—the sort of photo-op mishap that television loves to turn into a political metaphor. 

Remarkably, the Washington-based Club for Growth, spent $1.73 million—more than twice the amount spent by the Mourdock campaign proper—to trash Lugar as a tax-and-spend bipartisan moderate who was “President Obama’s favorite Republican.” Painfully for Lugar, the Club for Growth is headed by former Indiana congressman Chris Chocola, a former friend and ally.

Lugar’s defeat sends a chilling message to incumbents of both parties that the voters are in a sour mood and sick and tired of the same old faces—especially to his fellow six-term Republican Sen. Orrin Hatch, who is facing tough primary opposition in Utah.

The 60-year-old Mourdock's coming campaign against Donnelly will be bitter and bloody, as the Democrats try desperately to pick up a Senate seat in Indiana and thus mitigate expected losses elsewhere, such as vulnerable seats in Missouri and Montana, and hold on to a slim control of the Senate.

Donnelly, 56, a centrist Dem, will attempt to portray Mourdock as this year’s answer to Sharron Angle and Christine O’Donnell—two Tea Partiers who beat establishment Republicans in the Nevada and Delaware Senate primaries of 2010 but were ultimately judged too extreme and eccentric to win high office. O’Donnell famously ran a television ad in which she stated, “I’m not a witch.”

Or maybe Mourdock is this cycle’s Ken Buck. Even before the Hoosier polls closed, the Democratic Senatorial Campaign Committee issued a press release likening Indiana’s Republican Senate nominee to the loose-lipped Colorado Tea Party candidate who suggested primary voters support him over Lt. Gov. Jane Norton because “I don’t wear high heels.” Buck lost to incumbent Democrat Michael Bennet.

It might difficult, however, to shoehorn Mourdock into the role of Tea Party wacko. A veteran of elective politics, he has won statewide office twice and has run a disciplined Senate campaign with few mistakes.

“I think he will beat Donnelly,” Souder said. But Lugar has already written the opening chapter of the Democrats' playbook.