When Donald Trump announced he had won the presidency at his “victory party” in New York, he was surrounded by his family and Republican allies, urging for a united front for the American people.

Former New York City Mayor Rudy Giuliani, New Jersey Governor Chris Christie, Mr Trump’s Vice President-elect Mike Pence and even Republican National Committee chairman Reince Priebus were there to support and clap for the real estate mogul.

The on-stage line-up presented the face of a unified party. And the Republicans have many reasons for cheer. The election gave Republicans another four years at the helm of the House of Representatives and the Senate.

Now the Republican party is at its strongest in more than seven decades, when Harry S Truman was President.

Yet behind the scenes the party is split down the middle, as Mr Trump’s heated rhetoric took his colleagues by surprise over the past 18 months and exposed their detachment from the frustrations and concerns of their core voters.

The victory is likely to be bittersweet for newly re-elected Wisconsin representative and House Speaker Paul Ryan. He will be pleased that Bernie Sanders will not gain control of the treasury committee after all, but he said about a month ago that he would no longer defend Mr Trump after a leaked video from 2005 showed the next president bragging about his "right" as a celebrity to grab women by the genitals. On the campaign trail, Mr Ryan kept a wide berth from him.

“I want to congratulate Donald Trump on his incredible victory,” said Mr Ryan in a statement. “It marks a repudiation of the status quo of failed liberal progressive policies. We are eager to work hand-in-hand with the new administration to advance an agenda to improve the lives of the American people.”

After voting on Tuesday, some Republicans made their voices of opposition heard.

South Carolina Senator Lindsey Graham announced on social media that he cast his ballot for independent candidate Evan McMullin, the former CIA operative and banker who won more than a quarter of the state’s votes. Mr Graham's vote was significant as it broke the pledge that all of the 17 Republican candidates signed to support the party nominee.

Echoing other Republicans, Arizona senator Jeff Flake recently said the Trump approach was a “demographic cul-de-sac” and that “blaming every closed factory on trade deals” was unrealistic.

George W Bush phoned to congratulate the new president on Wednesday morning, despite reports that he had not supported him. Most of the Bush family, including George H W Bush, said they would not vote for the Republican.

“Trump has smoked out the rats in the Republican Party – the globalist rats,” said Tennessee Senator Frank Niceley claimed Mr Trump has “smoked out the globalist rats” from the party, as reported by the Alaska Dispatch News.

Round-up: Donald Trump wins US presidential election

“The Romneys, the Bushes, the [Gov. Bill] Haslams have all been controlled by the David Rockefeller globalist wing of the party.

“There's still those of us who believe in limited government and lower taxes, and we’re not going back. When you don’t back the nominee, you're done for,” he said.

Trump surrogate Omarosa Manigault, a former contestant of reality show The Apprentice, told the Independent Journal Review that the next president will keep a list of Republicans who voted against him.

“If [Graham] felt his interests was with that candidate, God bless him," said Ms Manigault. "I would never judge anybody for exercising their right to and the freedom to choose who they want. But let me just tell you, Mr. Trump has a long memory and we’re keeping a list.”

What will it mean to be a Republican now? The traditionally business happy party is in jeopardy as Mr Trump plans to tear up trade deals, slap on import tariffs, and break up big company deals that put power “in the hands of too few”. He will, however, slash corporation tax by 50 per cent.

Strategist Ana Navarro said the party was divided, along both party and colour lines.

“He won this race by dividing America,” she said, claiming there was one country for white America and another for people of colour.