Donald Trump took aim at Hillary Clinton for her use of a private email server while she was US secretary of state. (Reuters photo)
US Republican candidate Donald Trump is testing out themes to use against Democratic front-runner Hillary Clinton as he tries to persuade reluctant members of his party to get behind him for the November 8 presidential election.
Some top Republican leaders - US House Speaker Paul Ryan among them - are still expressing wariness about Trump but he is hoping to entice more support from Republicans by highlighting their common opponent.
On Friday, Trump took aim at Clinton for her use of a private email server while she was US secretary of state. Clinton has said she did not send or receive information marked as classified. The FBI is investigating whether laws were broken.
"The email scandal should take her down but I don't think it's going to because I think she's being protected by the Democrats," Trump said on "Fox & Friends," a television news program that attracts a large conservative viewership.
Trump tried to cast Clinton as weak on the economy, which is sure to be one of the main policy issues as the November 8 election approaches.
"If you look at what she's going to do, she's going to be so bad on jobs that wages are going to go down for workers," he said.
Paul Manafort, a top Trump advisor, told MSNBC that Republicans will rally behind the presumptive Republican nominee because he has strengthened the party by attracting new supporters.
"We want to unify the party, but the important thing to remember is Donald Trump just won a historic victory among 17 other candidates," Manafort said. "He is a very strong nominee. His vision that he laid out is not something in question."
Clinton has a higher probability than Trump of becoming the next president, but the gap between the pair narrowed this week, according to the online political stock market PredictIt.
Clinton's probability on Friday was 61 per cent, down from 65 per cent seven days ago, according to the site. The probability that Trump will win in November was 40 per cent, up from 34 per cent.
Republican Chairman Reince Priebus has already begun his efforts to rally behind Trump, saying at an event hosted by Politico that behind the scenes the candidate is "more gracious and personable than I think you see at rallies."
"I think there's work on tone to do," Priebus said, adding that he has made that point to Trump recently. "I think he gets it. I think you're going to see it. I think you're going to see the change in tone."
In addition to changing tone, Trump also faces an uphill climb to bring the party together. Ryan, the top elected Republican in the United States, said on Thursday he was not ready to support Trump, a sign of lingering establishment concern about the candidate's position on immigration and trade.
Trump took issue with Ryan.
"Paul Ryan said that I inherited something very special, the Republican Party," Trump wrote on Twitter. "Wrong, I didn't inherit it, I won it with millions of voters."
Trump Surprised By RyanIn the Fox interview, Trump said he was "very, very surprised" by Ryan's reluctance.
"I mean he talks about unity but what is this about unity?" he said. "And with millions of people coming into the party, obviously I'm saying the right thing."
Trump said he expected to meet with Ryan next week.
At a rally in West Virginia on Thursday night, the billionaire businessman criticized Clinton for the amount of money that she and her husband, former President Bill Clinton, accepted for the Clinton Foundation, which he called a "scam."
The foundation provides assistance to poor areas around the world. Critics have said the organization failed to disclose potential conflicts of interest by naming all donors when raising money for the foundation while Hillary Clinton was secretary of state. The Clintons have dismissed criticisms of the charitable organization as politically motivated, pointing to the positive work the foundation has dons around the world.
Trump also linked her to some of her husband's decisions when he was president in the 1990s, such as the NAFTA agreement that opened up trade among the United States, Mexico and Canada. Trump has vowed to rewrite trade deals if elected.
"We cannot take Hillary Clinton anymore," he said. "NAFTA was given to us by Clinton. We can't take any more of the Clintons."
In a sign some Republicans are rallying around Trump, Nebraska Governor Pete Ricketts, whose family has helped bankroll an anti-Trump group, is set to endorse him on Friday.
Former Texas Governor Rick Perry, who last year described Trump as a "cancer on conservatism" while running against him for the Republican nomination, supported him as well.
Trump's effort to raise as much as $1 billion for his campaign and the Republican Party for the general election is just getting started and got a boost on Thursday when billionaire casino owner Sheldon Adelson announced his support for Trump.
Trump's new finance chair Steven Mnuchin said he is confident of raising money.
"I literally got hundreds of emails and hundreds of calls yesterday from all different kinds of people in finance, in the financial markets, people who run companies, people who run hedge funds," he told CNBC on Friday.
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