By Steve Holland and Emily Flitter

(Reuters) - Republican candidate Donald Trump overhauled his presidential campaign team on Wednesday for the second time in under two months, hiring the head of a conservative news website to bolster his combative image and try to reverse poor opinion poll numbers.

Trump named Steve Bannon, head of the Breitbart News website, as campaign chief executive officer, a new position. He also promoted senior adviser Kellyanne Conway to the post of campaign manager.

The latest shakeup combines Bannon, a conservative flamethrower, with Conway, a measured, data-driven analyst who might be able to broaden Trump's appeal to women and independent voters.

It offers Trump's team a chance to return to the "let Trump be Trump" style practiced by former campaign manager Corey Lewandowski in winning the Republican presidential nomination for the Nov. 8 election.

Lewandowski, ousted in the last campaign reorganization in June, said on CNN that Bannon was "a street fighter" like himself. A Trump campaign statement announcing the changes touted a Bloomberg Politics article that branded Bannon "the most dangerous political operative in America."

Whether this style will work in the fight against Democratic candidate Hillary Clinton is unclear. Trump, a New York real estate developer and former reality TV host, has largely been unable to extend his reach beyond white middle-class voters who pack his rallies.

Trump is behind Clinton in national opinion polls and in many battleground states, potentially facing a big defeat that could also cost Republicans congressional races.

Trump, who relishes revving up crowds with off-the-cuff remarks, drew criticism for comments insulting women, Muslims and Mexican immigrants during the primary campaign for the Republican nomination.

Since then, he has faced a barrage of criticism from Republicans over his campaign style and his refusal to stick to a policy message. In particular, he has been rebuked for his prolonged feud with the family of a Muslim U.S. Army captain who was killed in the Iraq war.

Wednesday's appointments amounted to a demotion for Paul Manafort, who was brought on as campaign manager in June to bring a more professional touch to Trump's campaign but has struggled to get the businessman to rein in his freewheeling ways.

Clinton, a former secretary of state who has called Trump temperamentally unsuited for the White House, said staff shake-ups do nothing to change the candidate and his rhetoric.

"Donald Trump has shown us who he is, he can hire and fire anybody he wants from his campaign, they can make him read new words from a teleprompter, but he is still the same man who insults Gold Star families, demeans women, mocks people with disabilities and thinks he knows more about ISIS than our generals," she told a rally in Ohio.

DIFFERENT STYLES

Conway and Bannon may prove to be opposing forces in Trump’s campaign. Conway is analytical and numbers-driven and often offers a more pragmatic approach to winning campaigns. She is expected to travel with Trump. Bannon likes to push the limits of polite conversation and revels in taking the fight up a notch, strategists say.

"For Steve and I, we also recognize that we are different when we say we have different styles, but we have one vision," Conway told reporters.

Bannon was a key figure in producing and promoting a movie called "Clinton Cash" that accuses Bill and Hillary Clinton of doing favors for high-dollar donors to the Clinton Foundation charity, a theme that Trump has been touching on in his campaign speeches.

"My guess is Bannon will be a bull in a china shop and Conway will be focused on messaging and paid media," said Republican strategist Matt Mackowiak.

The appointment of Bannon suggested that Trump is aiming not to tone down his aggressive style but to be more disciplined in emphasizing themes that resonate strongly with the voters he is trying to court, such as his tough stance against illegal immigration and withering personal criticism of Clinton.

"I am who I am, I don’t want to change," Trump told Wisconsin television station WKTB on Tuesday. "If you start pivoting, you’re not being honest with people.”

The shift to new leadership may not be a good sign at this stage of a campaign, but some Republican strategists stressed that it was not too late for Trump.

"I've thought for a while that they've needed more smart, senior people and it looks like they just got them," said Republican strategist Charlie Black. "It's only the middle of August. This race is going to be close in the end, but he does need to tighten up his performance."

Conway told Fox News she was advising Trump, who has never held elected office, to “keep giving policy speeches," saying voters want to hear more than “cacophony.”

She said she was also advising him to take “his case directly to the people.” “With Donald Trump, he is still his own best messenger because people see him as very authentic,” she said.

A New Jersey-based pollster, Conway has worked in Republican polling since the 1980s, including for former House of Representatives Speaker Newt Gingrich’s unsuccessful presidential campaign in 2012. She also worked for vice presidential nominee Mike Pence in his earlier races.

Conway has worked to improve the Republican Party's standing with women voters and to push back on the Democratic accusations that Republicans are waging a "war on women."

Manafort, who will remain on the campaign but will see his influence scaled back, drew unwelcome attention this week when The New York Times reported that his name was on secret ledgers showing cash payments designated to him of more than $12 million from a Ukrainian political party with close ties to Russia. Manafort denied any impropriety on Monday.

The source also said Trump was less concerned than his children were about Manafort's Russia ties. The news reports about Manafort's relationship with Ukrainian officials could have been "the last straw," but the biggest problem was that Trump did not trust Manafort's advice, the source said.

The current RealClearPolitics average of national opinion polls puts Clinton six percentage points ahead of Trump, at 47.2 percent to his 41.2 percent.

Trump was scheduled to receive an intelligence briefing on Wednesday afternoon from the Office of the Director of National Intelligence, a U.S. government source said.

The briefing, of the kind given to U.S. presidential nominees from major parties, was to take place in a secure conference room at the New York Field Office of the Federal Bureau of Investigation in downtown Manhattan.

Intelligence officials brief the nominees on foreign policy and national security issues but do not disclose ultra-sensitive information about ongoing U.S. undercover spy operations, or about the identities of intelligence sources and methods.

(Additional reporting by Alana Wise, Amanda Becker, Ginger Gibson, Luciana Lopez and Mark Hosenball; Writing by Alistair Bell; Editing by Frances Kerry and Jonathan Oatis)