WASHINGTON – Donald Trump consolidated his lead in the 2016 Republican presidential race with Super Tuesday victories but failed to eclipse his rivals or draw reluctant party leaders into his corner.
The New York real estate tycoon proclaimed himself a "unifier" on Tuesday night after he won seven states from centrist Massachusetts to the conservative Deep South. That fell on deaf ears as his White House rivals were unbowed and the Republican establishment unwilling to accept him as their standard-bearer in the November 8 race to replace Democratic President Barack Obama.
"If this was anybody else as a front-runner, there'd be people right now saying 'Let's all rally around the front-runner,'" said US Senator Marco Rubio of Florida, who won his first state contest, Minnesota, on Tuesday.
"That will never happen with Donald Trump," Rubio, favourite of the Republican establishment, told Fox News on Wednesday. "On the contrary."
The Super Tuesday wins cemented Trump's front-runner status. The 69-year-old political newcomer went into the busiest day of the primary season with a hefty lead in national opinion polls and victories in three of the first four Republican contests.
His latest wins also compounded the problem for a party whose leaders are both critical of many of Trump's positions and values and sceptical he can defeat the likely Democratic nominee in November, former secretary of state Hillary Clinton.
While they have yet to coalesce around a single strategy, anti-Trump Republicans have begun taking action.
Conservative advocacy group Club for Growth claimed credit for slowing Trump in some primary states by running attack ads.
Some party donors – including hedge-fund manager Paul Singer and Meg Whitman, the Hewlett-Packard Enterprise chief executive – organised a phone call on Tuesday to get funding for an anti-Trump effort, the New York Times reported.
Democrats pounced on the chaos. Senate Minority Leader Harry Reid called Trump a "monster" the Republicans spawned with their years of rancorous opposition to all major Obama administration initiatives.
"Republicans created him by spending seven years appealing to some of the darkest forces in America," Reid said on the Senate floor on Wednesday.
On the Democratic side, Clinton, 68, took big steps toward securing her party's nomination on Tuesday, the 2016 campaign's biggest day of state-by-state nominating contests.
Her victories in seven states were propelled by African-American voters in southern states like Arkansas, where she and her husband, former president Bill Clinton, began their political careers.
Clinton's rival, US Senator Bernie Sanders, won his home state of Vermont along with Colorado, Minnesota and Oklahoma but lost to her in Massachusetts, which he had hoped to win.
The democratic socialist vowed to pursue the battle for the nomination in the 35 states yet to vote.
Trump's main rivals, Senator Ted Cruz of Texas and Rubio, 44, said they were determined to remain in the race.
Cruz, 45, won Texas and Oklahoma, as well as the Alaska caucuses, bolstering the conservative senator's argument that he has the best chance of stopping Trump.
Trump dismissed furious criticism aimed at him by establishment Republicans during his victory speech in Florida on Tuesday night.
Facing strong party disapproval over his ideas to build a wall between the US and Mexico, deport 11-million illegal immigrants and temporarily bar Muslims from entering the country, Trump declared he had expanded the party by drawing in disaffected blue-collar Democrats who like his tough-on-trade rhetoric.
"I am a unifier," he said. "I would love to see the Republican Party and everybody get together and unify, and when we unify, there's nobody that's going to beat us."
The country's top two elected Republicans, House Speaker Paul Ryan and Senate Majority leader Mitch McConnell, chastised Trump this week over his delay in disavowing an endorsement by David Duke, a former leader of the white supremacist Ku Klux Klan.
"I've disavowed," Trump said. "I'm going to get along with Congress, okay? Paul Ryan, I don't know him well, but I'm sure I'm going to get along great with him.
"And if I don't, he's going to have to pay a big price, okay?" the former reality TV star added in remarks that could further inflame party tensions.
Ryan's press representatives said they would not comment.
For Rubio, Tuesday was a day of reckoning. His losses piled up after a week in which he tried to tackle Trump on his own terms, calling Trump a "con artist" and lobbing crude taunts.
Suddenly, the March 15 contest in Florida loomed over Rubio as a must-win.
"Florida, I know you're ready," Rubio said. "The pundits say we're underdogs. I'll accept that. We've all been underdogs."