Cleveland – Portions of Melania Trump's prime-time speech to the Republican National Convention on Monday appear to have been plagiarised, tarnishing what should have been her big moment to introduce herself to the American public.The apparent plagiarism came to light shortly after the 46-year-old former model took to the stage with husband Donald Trump on Monday night, to offer an eloquent testimonial of his strengths as a husband, father, and potential leader of the United States.A section of the speech describing the values that shaped her life strongly resembled a passage from Michelle Obama's speech to the 2008 Democratic convention."My parents impressed on me the values: that you work hard for what you want in life. That your word is your bond and you do what you say and keep your promise. That you treat people with respect. They taught me to show the values and morals in my daily life. That is the lesson that I continue to pass along to our son," Melania Trump said."And we need to pass those lessons on to the many generations to follow. Because we want our children in this nation to know that the only limit to your achievements is the strength of your dreams and your willingness to work for them."Presidential candidateIn her speech, Michelle Obama said: "And Barack and I were raised with so many of the same values: that you work hard for what you want in life; that your word is your bond and you do what you say you're going to do; that you treat people with dignity and respect, even if you don't know them, and even if you don't agree with them."And Barack and I set out to build lives guided by these values, and pass them on to the next generation. Because we want our children – and all children in this nation – to know that the only limit to the height of your achievements is the reach of your dreams and your willingness to work for them."Melania Trump's speech was the highlight of a chaotic opening day of a Republican convention that is set to formally nominate her husband as the party's presidential candidate later this week.A beaming Trump personally introduced his wife to the cheering delegates gathered in Cleveland, breaking with tradition by appearing before his actual nomination."It was truly an honour to introduce my wife, Melania. Her speech and demeanour were absolutely incredible. Very proud!" the billionaire tweeted afterwards.