In the end, the unstoppable force of Rep. Henry Waxman (D-Calif.) overwhelmed the immovable object of Rep. John Dingell (D-Mich.).

The Californian harnessed the change theme that electrified Democrats on Election Day and rode it to victory in his surprise bid for Dingell’s post at the helm of the Energy and Commerce Committee.

Waxman won on a 137-122 vote of the House Democratic Caucus.

The vote marked a stunning rebuke of the seniority system that Democrats have honored for decades. It also constituted a win, of sorts, for Speaker Nancy Pelosi (D-Calif.) — who is ideologically aligned with Waxman and has clashed repeatedly with Dingell — as she continues to consolidate power.

Though Pelosi steered clear of any involvement in the race herself, Rep. George Miller (D-Calif.), one of her top lieutenants, helped lead the charge for Waxman.

And at least one prominent Dingell backer, Ways and Means Chairman Charlie Rangel (D-N.Y.), suggested that Waxman’s gambit had Pelosi’s tacit approval. “I assume that not playing a role is playing a role,” he said after the vote.

For all the uncertainty of a secret ballot election in a contest that divided the Caucus along geographic, ideological and deeply personal lines, Waxman’s camp entered the Cannon House Office Building Caucus Room on Thursday morning confident a win was at hand, aides to Waxman’s supporters said. They believed they had wrapped up commitments from a simple majority of Democrats by the end of last week and spent this week shoring up that roster and padding it with new names.

A key bloc of votes for Waxman appears to have come from incoming freshmen, who had no existing loyalty to either contender but responded to a pitch from Waxman’s team that his bid represented an extension of President-elect Barack Obama’s change message.

“Part of the pitch was, ‘We’ve been hungering for new opportunity, and this is our opportunity,’” one aide to a Waxman supporter said.

Waxman’s supporters pressed that point in speeches to the Caucus Thursday morning, with one-term Rep. Bruce Braley (D-Iowa) surprising some with a direct attack on Dingell’s tenure.

Dingell supporters, on the other hand, touted the incumbent chairman’s effectiveness at the panel’s helm and appealed to their colleagues to respect length of service. Rep. John Lewis (D-Ga.) invoked the golden rule — asking lawmakers to do unto others as they would have done to them — in arguing that the seniority system deserves to be honored, sources in the room said.

Reverence for seniority failed to carry the day, and the result raised questions about the status of other long-serving chairmen — Dingell’s fellow “Old Bulls” who have already seen their power eroded as Pelosi has repeatedly seized the initiative from them over the past two years.

It was a fact not lost on the chairmen themselves, most of whom lined up behind Dingell. Asked about the seniority system in the wake of Dingell’s toppling, Rangel said, “It has just been buried.”

But Waxman, addressing reporters after his win, suggested the tradition should not be mistaken for an entitlement.

“Seniority is important, but it should not be a grant of property rights to be chairman for three decades or more,” he said.

Rep. Jim Cooper (D-Tenn.), who broke with fellow senior members of the Blue Dog Coalition to back Waxman, said the seniority argument had been overblown. “It’s an argument of convenience, like states’ rights. Nobody really believes it,” he said. “We don’t own these jobs. These jobs are a gift from the Caucus. Dingell is one of the all-time greats, but that doesn’t mean you get 30 years. He got 28 years.”

Cooper said the contest “boiled down to, ‘Do you want the best quarterback or the oldest quarterback?’”

Cooper notwithstanding, the oldest quarterback counted most moderates among the members of his squad. For that group — which includes Blue Dogs and members of the business-friendly New Democrat Coalition — Dingell’s defeat compounded what they view as an alarming leftward shift in the Caucus. It was set in motion in the days after the election, as Pelosi moved to help her loyalists lock up leadership posts. “The whole movement is to the left,” said one moderate Democrat leaving the vote Thursday morning.

The centrist wing of the party has been quietly arguing that they deserve better treatment, especially considering that Democrats from conservative districts have delivered the party its expanded margin in the House.

Following the vote, many of those Dingell backers were visibly shell-shocked by the resounding defeat their colleagues handed the dean of the House.

“I can’t believe we just did what we did,” said Rep. Stephanie Herseth Sandlin (D-S.D.), a Blue Dog and whip for Dingell.

It remains to be seen whether they will make an outright appeal for a new leadership slot or some other formal recognition of their numbers from the Speaker. “It’s going to take a little while to step back and figure it out,” the lawmaker said.

Likewise, the path forward for Dingell was not immediately clear. After the vote, he huddled with his staff and thanked them for their efforts, sources familiar with the session said. Dingell said he was proud of them and would help them find new jobs, and then he went home.

Sources close to Dingell said he has not begun to think about what role he wants to play next. Pelosi on Thursday named him chairman emeritus — an apparently ceremonial role that will allow him to keep office space in the Capitol. As the panel prepares to tackle major pieces of Obama’s agenda, Dingell can still wield his seniority — unrivaled in the House — to claim first dibs on an Energy and Commerce subcommittee gavel. That would require displacing a sitting subcommittee chairman, who could challenge Dingell for the post, though that is an unlikely scenario, given most panel members’ reverence for the 27-term lawmaker.

Securing a post leading the subcommittee on Energy and Air Quality or Health would mean a reduced but still significant portfolio for Dingell as Congress gears up for major debates on climate change and health care reform. Dingell signaled he intends to get back to work in a statement after the vote that recognized the spirit of change had prevailed. “Well, this was clearly a change year and I congratulate my colleague Henry Waxman on his success today. I will work closely with him on the issues facing the Energy and Commerce Committee and for a smooth transition,” he said.

Either way, Dingell has some time to think about his next move, since the makeup of the committee will not be decided until lawmakers begin organizing early next year.

Waxman’s win means he will give up the reins of the Oversight and Government Reform Committee, and his replacement is uncertain. The second-ranking member, Rep. Edolphus Towns (D-N.Y.), appears to be in line. He has declared his interest in the gavel and said that he anticipates wide-ranging support from the Caucus and is prepared to mount a “vigorous campaign.”

The Democratic Steering and Policy Committee is expected to meet as soon as next month to endorse a candidate for the job.

Steven T. Dennis contributed to this report.