Cleveland - Hillary Clinton moved closer to introducing her running mate, snatching attention from newly crowned Republican nominee Donald Trump just hours after he closed out his convention with a fiery and foreboding turn at the podium.Crews were still sweeping confetti from the GOP convention hall floor, as the Clinton campaign signalled an announcement was coming soon. In a tweet on Friday morning, her campaign urged supporters to text the campaign to get word first. Virginia Sen. Tim Kaine had emerged as the leading contender, according to Democrats familiar with Clinton's search.The news could quickly steal Trump's thunder. In a 75-minute speech on Thursday night, Trump made forceful promises to be the champion of disaffected Americans, capping his convention on a high note for the party, not a moment too soon after shows of disharmony and assorted flubs before the four-day closer.Speaking to "the forgotten men and women of our country," the people who "work hard but no longer have a voice," he declared: "I am your voice." With that, he summed up both the paradox and the power of his campaign - a billionaire who made common cause with struggling Americans alienated from the system, or at least a portion of them.The speech was strikingly dark for a celebratory event and almost entirely lacking in policy details. Trump pledged as president to restore a sense of public safety, strictly kerb immigration and save the nation from Clinton's record of "death, destruction, terrorism and weakness.""I have joined the political arena so that the powerful can no longer beat up on people that cannot defend themselves," Trump said. He shouted throughout as he read off a teleprompter, showing few flashes of humour or even smiles.Democrats offered a different assessment, with Clinton campaign chairperson John Podesta arguing that Trump "offered no real solutions to help working families get ahead or to keep our country safe, just more prejudice and paranoia. America is better than this. America is better than Donald Trump."Clinton opens a two-day campaign swing on Friday in Florida and is expected to introduce her running mate either at a Friday afternoon rally at the state fairgrounds in Tampa or on Saturday at Florida International University in Miami.Kaine, 58, appeared to be the favourite for her choice, according to two Democrats, who both cautioned that Clinton has not made a decision and could change direction.Republicans relentless in demonising ClintonIn Cleveland, Trump's acceptance of the Republican nomination capped his improbable takeover of the GOP, a party that plunges into the general election united in opposition to Clinton but still torn over Trump. Underscoring his unorthodox candidacy, Trump reasserted the hard-line immigration policies that fired up conservatives in the primary but broke with many in his party by expressing support for gays and lesbians.Ever the showman, he fed off the energy of the crowd, stepping back to soak in applause and joining the delegates as they chanted, "U-S-A."It was an altogether smoother - and more scripted - chapter in a footloose convention shocked a night earlier by Ted Cruz's prime-time speech, a pointed non-endorsement of the nominee by the Texas senator who finished second in the race and came to Cleveland harbouring grievances — and future presidential ambitions.During their convention, Republicans were relentless and often raw in demonising Clinton. As fired-up supporters at Trump's acceptance speech broke out in their oft-used refrain of "Lock her up," the nominee waved them off, and instead declared, "Let's defeat her in November." Yet he also accused her of "terrible, terrible crimes.""This is the legacy of Hillary Clinton: death, destruction, terrorism and weakness," he said. "But Hillary Clinton's legacy does not have to be America's legacy."In a direct appeal to Americans shaken by a summer of violence at home and around the world, Trump promised that if he takes office in January, "safety will be restored."He also said young people in predominantly black cities "have as much of a right to live out their dreams as any other child in America." And he vowed to protect gays and lesbians from violence and oppression, a pledge that was greeted with applause from the crowd."As a Republican, it is so nice to hear you cheering for what I just said," he responded.Democrats expected to be more orderlyThe Democratic convention in Philadelphia, which starts on Monday, is expected to be a more orderly affair. Clinton is, if anything, disciplined.Kaine has been active in the Senate on foreign relations and military affairs and built a reputation for working with both parties as Virginia's governor and mayor of Richmond."I'm glad the waiting game is nearly over," Kaine said on Thursday.Agriculture Secretary Tom Vilsack, a long-time friend of Hillary and Bill Clinton, is still in the mix, according to one of the two Democrats. Both Democrats are familiar with the selection process and spoke on the condition of anonymity because they were not authorised to discuss it publicly.Kaine's selection would not be without complication. Liberals have expressed wariness of Kaine for his support of putting the Trans-Pacific Partnership trade agreement on a "fast track" to approval, which both Clinton and primary rival Bernie Sanders oppose. They also note that Kaine recently signed onto a letter asking for less burdensome regulation of regional banks.