WASHINGTON (AP) — Republicans assumed full control of Congress on Tuesday for the first time in eight years in a day of pomp, circumstance and raw politics beneath the Capitol Dome. “We will get to work right away,” pledged House Majority Leader Kevin McCarthy, R-Calif.

As required by the Constitution, Congress convened at noon. On the Senate floor, newcomers mixed with veterans as, with Vice President Joe Biden presiding, Mitch McConnell of Kentucky was automatically ascended to majority leader following the approval of rank-and-file Republicans last year.

Across the Capitol in the House, a similar scene unfolded as familiar faces and new ones crowded the aisles and lawmakers of both parties recited the Pledge of Allegiance. But in the House, there was an element of slight suspense as Speaker John Boehner of Ohio faced a tea party-backed effort to unseat him, though it looked certain to fall short.

Seeking unity despite the internal party dissension, the GOP moved swiftly toward a veto showdown with President Barack Obama over the long-stalled Keystone XL pipeline, a taste of things to come in divided government.

At the White House, Obama planned to meet with the new congressional leadership next week as both sides positioned themselves for two years of clashes and, perhaps, occasional cooperation that will help shape the outcomes of the 2016 presidential and congressional elections.

McConnell replaces Democrat Harry Reid of Nevada, who was a surprise no-show from the day’s proceedings after he injured himself exercising.

Reid, who broke several ribs and bones in his face when a piece of equipment snapped last week, said his doctor had ordered him to work from home Tuesday. A photo Reid posted to Twitter showed him with his right eye taped over as he met with lawmakers.

Newcomers and veterans alike were to raise their hands to swear the oath of office, many with spouses, children and grandchildren looking on to witness the biennial display of pageantry. The spectacle drew political veterans back to the Capitol as former Vice President Walter Mondale, a Democrat, and former Senate Majority Leader Bill Frist, a Republican, mixed with lawmakers on the Senate floor.

McConnell and Boehner both were to deliver remarks as they began laying down markers for legislative battles ahead.

First, Boehner had to survive his re-election as speaker — the main event on any opening day’s agenda. Tea party-backed Reps. Louie Gohmert of Texas and Ted Yoho of Florida put themselves forward as challengers to Boehner, and more than a dozen Republicans announced they would oppose Boehner.

The ranks of the opponents grew in the hours ahead of Tuesday’s vote, but appeared to remain short of the number needed to place Boehner’s election in jeopardy. Many lawmakers dismissed the challenge as a needless distraction at a moment when the party should be celebrating new majorities and showing voters it can lead.

“It’s time to put all this silliness behind and move on,” said Rep. Phil Roe, R-Tenn. “We’re on probation. If we don’t perform ... (voters) can make a pivot in a heartbeat.”

Nor did any of the rebels predict they would succeed in toppling the 65-year-old Boehner. Instead, they said the current high command wasn’t conservative enough.

For his part, Yoho said the initial goal of the Boehner challenge is to force the leadership contest past one ballot, so there could be a serious discussion about change.

“I think we need to articulate a vision for the country, a vision for this conference,” he told reporters late Monday. “I threw my hat into the ring so people could have a choice and an alternative.”

But Boehner’s hand is strong after the Republicans’ sweeping electoral triumph. The party will hold 246 House seats in the new Congress, to 188 for the Democrats, the biggest GOP majority in nearly 70 years.

Coupled with the commanding majority was word of the first retirement — New York Republican Chris Gibson announced he would step down at the end of his term, but signaled he was not finished with politics in his home state.

The intra-party leadership struggle underscored the political peril facing Republicans as they looked ahead to two-house control of Congress. Yet the evident ability to pass the Keystone pipeline legislation showed their potential to advance an agenda.

Votes in a Senate committee and on the House floor were scheduled for later this week on the pipeline, which passed the House but died in a Democratic-led filibuster in the Senate late last year. Now, Republicans appear to have more than enough votes to clear it through the Senate as well, given the Republican pickup of nine seats in the elections.

While Obama has not said if he will reject the measure, White House spokesman Josh Earnest outlined a series of concerns with the pipeline before adding, “I’m not prepared at this point to issue a veto threat related to that specific piece of legislation.”

But Republicans stand ready to cast the measure as a bipartisan jobs bill of the type that should be signed into law.

“There’s a lot we can get done together if the president puts his famous pen to use signing bills rather than vetoing legislation his liberal allies don’t like,” McConnell said late last year.

Earnest, meanwhile, was less ambiguous about another issue.

Referring to an assertion by a Louisiana reporter, he said Rep. Steve Scalise of Louisiana, the third-ranking House GOP leader, had once described himself as “David Duke without the baggage.” Earnest also said Scalise’s presence in the leadership of House Republicans “says a lot about who they are.”

Scalise spoke more than a dozen years ago to a white supremacist organization founded by Duke. The lawmaker said recently the appearance was a mistake and said he condemns the group’s views.

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Associated Press writers David Espo, Nedra Pickler, Chuck Babington and Stephen Ohlemacher contributed to this report.