By Emily Flitter and Emily Stephenson

NEW YORK/WASHINGTON (Reuters) - Donald Trump fired Corey Lewandowski, the campaign manager who helped him win the Republican Party's presidential nominating contests but clashed with other advisers on how to appeal to the broader general electorate, several people with knowledge of the decision said on Monday.

The firing on Monday morning was another shakeup for a campaign already at odds with many senior Republican figures over the presumptive nominee's policies, with the party's nominating convention in Cleveland less than a month away.

But it may also prove a step toward calming concerns among party leaders about Trump, a wealthy businessman and political outsider, and the conflicting advice he was getting from senior aides, as he battles presumptive Democratic nominee Hillary Clinton ahead of the Nov. 8 election.

Three people close to the campaign said some of Trump's staff viewed Lewandowski as opposing strategic changes and staff hires urged for the general election campaign by Paul Manafort, a strategist hired in April partly for his experience on presidential campaigns that Lewandowski lacked.

The three, a campaign staffer and two people in regular contact with Trump advisers, spoke on condition of anonymity because they were not authorized by Trump to discuss the firing.

Manafort will take over as campaign manager, said Carl Paladino, co-chairman of the campaign's operations in New York state.

"Paul's in charge," Sean Spicer, the Republican National Committee's communications director, said in an interview.

Trump's decision to fire his manager came in part at the urging of his daughter Ivanka Trump and her husband, Jared Kushner, who have powerful advisory roles in the campaign, the two people in contact with Trump aides said.

Hope Hicks, who single-handedly fields Trump's media inquiries, disputed reports she had complained about Lewandowski to Ivanka Trump. "That is entirely untrue," she said.

The Trump campaign confirmed only Lewandowski's departure, not the circumstances.

Lewandowski, 42, had been a near-constant presence at Trump's side since the New York developer launched his campaign on June 2015.

In a brief statement read on CNN, Lewandowski said: "I stand by the fact that Mr. Trump is a great candidate and is better than Hillary Clinton ever will be."

Lewandowski denied there were any tensions between him and Trump's family in an interview with CNN.

Later on Monday, a campaign adviser resigned after reveling in Lewandowski's exit on his Twitter account, CNN reported.

"Ding dong the witch is dead!" Michael Caputo, the adviser, wrote shortly after reports of the firing emerged. He later released a statement to CNN saying he had resigned. "In hindsight, that was too exuberant a reaction to this personnel move," his statement said.

CAMPAIGN TENSIONS

The RNC spokesman did not think there would be a change in Trump's tone. "It's going to be more of a streamlined effort and more of an understanding of the difference that a general election has," Spicer said.

Clinton's campaign has hundreds more staff than that of Trump. In contrast to her unsuccessful 2008 presidential bid, there has been no public sign this time of any significant infighting among her advisers.

The former U.S. secretary of state has also spent millions of dollars on television commercials in recent weeks. Trump has not aired any paid advertisements since becoming the presumptive nominee, preferring to spread his message through his Twitter account and in media interviews.

Trump has faced setbacks in the past two weeks. His renewed calls to temporarily ban Muslims from entering the United States have drawn heavy criticism from Republican politicians in Washington and prompted corporate sponsors like Apple and JPMorgan Chase to withhold funding from the party's July 18-21 convention. Recent opinion polls show at least half of all voters approve of the Muslim ban.

Lewandowski, a former New Hampshire field director for a conservative advocacy group, argued that Trump's unconventional campaigning style did not need to be changed after it proved successful in the last few months of primary contests.

Lewandowski repeatedly defended that strategy with a line that became his mantra: "Let Trump be Trump."

Known for his brusque manner, Lewandowski was accused of manhandling a female reporter in Florida during the primary campaign, but the battery charge against him was later dropped.

He is still scheduled to attend the Cleveland convention as chairman of New Hampshire's delegation.

The Democratic National Committee said Lewandowski's exit was unlikely to change Trump.

"It wasn't Corey Lewandowski who called for a ban on Muslims entering the United States," Mark Paustenbach, a party spokesman, said in a statement, "it was Donald Trump."

(Additional reporting by Doina Chiacu in Washington; Writing by Jonathan Allen; Editing by Jonathan Oatis and Peter Cooney)