South Carolina Governor Nikki Haley, viewed as a possible Republican vice presidential candidate, endorsed US Senator Marco Rubio on Wednesday for their party's 2016 White House nomination, three days before the state's presidential primary.
"If we elect Marco Rubio, every day will be a great day in America," Haley said with Rubio at her side at an event in Chapin, South Carolina.
Haley's endorsement gave Rubio, 44, a valuable ally to try to sway voters in South Carolina, the third contest after Iowa and New Hampshire to pick a party nominee for the Nov. 8 presidential election to succeed Democratic President Barack Obama.
Rubio is seeking to take second or third place in South Carolina's Republican primary on Saturday and potentially emerge as the main Republican establishment alternative to front-runner Donald Trump, who has a big lead in the state.
"I can't tell you how honored I am to get the support of your governor. We have a lot of good candidates in the field," Rubio told the crowd.
The endorsement came as a new wave of bickering broke out between Trump and US Senator Ted Cruz of Texas, who is in second place in the polls in South Carolina. Trump threatened to sue Cruz over an anti-Trump TV ad that expressed doubts about Trump's statement he is a conservative.
Cruz, Rubio and retired neurosurgeon Ben Carson were to appear at a CNN town hall in Greenville, South Carolina, on Wednesday evening, with Trump on MSNBC about the same time.
Blow to Bush
The daughter of Indian immigrants, Haley, 44, seized the spotlight in January when in the Republican response to Obama's State of the Union speech, she set herself apart from the party's presidential candidates by calling for tolerance on immigration and civility in politics.
Last year, she gained national attention by leading an effort to remove the Confederate battle flag from the state Capitol grounds after the killing of nine black churchgoers in Charleston. The Civil War-era emblem of the Confederate South is long associated with slavery.
Some political analysts have said she could be picked as the Republican vice presidential nominee.
Haley's endorsement of Rubio was a blow to the candidacy of former Florida Governor Jeb Bush, coming two days after Bush's brother, former President George W. Bush, met with Haley privately in the state capital, Columbia.
A Bush aide said Haley called Bush to inform him of her plan to endorse Rubio.
"Disappointed" was Bush's response to the endorsement. "She's a very good governor and should I win the nomination, there'll be a role for her in the campaign," Bush, 63, told reporters after a campaign event in Summerville, South Carolina. "Trust me, she's a great person."
At a town hall meeting in Summerville, Bush took advice from the audience on how he might better conduct his campaign. Some of the advice was conflicting.
Edward Scott, who works in South Carolina but lives in Frederick, Maryland, told Bush he should consider not responding to attacks from Trump, while another man asked Bush whether he should be tougher, a "sumbitch" as he called it.
David Villinger of Summerville said Bush should focus less on his record as Florida's governor and more on his presidential vision. "I would encourage you to go not just on your record but on your plan," he said.
Bush said he would not stop responding to Trump and vowed to have a toughness of spirit.
Cruz, Trump clash anew
Ahead of Saturday's Republican vote, Cruz and the billionaire businessman Trump battled for votes with an exchange of harsh words. Cruz, 45, won the first Republican nominating contest in Iowa on Feb. 1 and Trump, 69, won the second one in New Hampshire on Feb. 9.
Cruz dared Trump to sue him over a campaign ad featuring a 1999 video clip of the former reality TV star saying he was "very pro-choice" on abortion. In the clip, Trump said he would not ban late-term abortions.
Cruz said Trump sent his campaign a "cease and desist letter" demanding it drop the ad. "File the lawsuit," Cruz, a lawyer, told reporters on Wednesday, adding he would depose Trump himself.
"You have been threatening frivolous lawsuits for your entire adult life," Cruz said of Trump. "Even in the annals of frivolous lawsuits, this takes the cake."
Trump responded that he opposes abortion, which most US conservatives also do not support.
"These ads and statements made by Cruz are clearly desperate moves by a guy who is tanking in the polls - watching his campaign go up in flames finally explains Cruz's logo," Trump said in a statement, referring to the flame icon that appears on Cruz's website and elsewhere.
The real estate developer again hinted he might sue Cruz, who was born in Canada to a US citizen mother, over his eligibility to run for president.