On one of the biggest nights of the Democratic National Convention, President Barack Obama evoked the words of a Republican hero - former President Ronald Reagan. Obama repeatedly summoned Reagan's hope and optimism Wednesday night as Democrats try to attract disenchanted Republican voters uneasy about Donald Trump's claim to the GOP mantle and fearful about a possible presidency. As he made the case that Democrat Hillary Clinton is more qualified to serve in the White House, Obama drew a stark contrast with Trump's dark vision of the country. He reminded voters that Reagan famously called America ''a shining city on a hill.'' Trump, he said, calls the United States ''a divided crime scene'' and hopes to win votes by scaring people over immigration and crime. Evoking Reagan is nothing new for Obama, who also praised the Republican when he was running for president eight years ago and drew plenty of heat from his own party for doing so. As Obama battled Clinton for the 2008 Democratic nomination, he lauded Reagan for changing ''the trajectory of America'' and said that Republicans ''were the party of ideas for a pretty long chunk of time.'' At the time, Hillary Clinton lambasted Obama for praising Reagan's legacy, saying the Republican had bad ideas that were bad for the country. But Obama insisted Democrats could disagree with Reagan's specific policies, yet still admire him as a transformative political figure who was able to win over many Democrats and independents. He said Democrats needed to think in the same way if they had any hope of reclaiming the presidency. Fast forward to Wednesday night, and Obama was at it again. He said the rhetoric at the GOP convention in Cleveland ''wasn't particularly Republican, and it sure wasn't conservative.'' ''The America I know is full of courage, and optimism, and ingenuity,'' Obama said. ''The America I know is decent and generous.'' Obama criticized Trump for calling the U.S. military ''a disaster'' and suggesting the nation is weak. He said Trump's gloomy vision was ''selling the American people short.'' ''America is already great,'' Obama said. ''America is already strong. And I promise you, our strength, our greatness, does not depend on Donald Trump.'' Former Reagan speechwriter John Podhoretz, now editor of the conservative Commentary magazine, took note on Twitter of the similarities between Obama's remarks and Reagan. ''Take about five paragraphs out of that Obama speech and it could have been a Reagan speech,'' he tweeted. ''Trust me. I know.'' Rich Lowry, editor of National Review, made a similar observation. ''American exceptionalism and greatness, shining city on hill, founding documents, etc. -they're trying to take all our stuff,'' he tweeted. Shortly before Obama spoke, Democrat-turned-Republican-turned-independent Michael Bloomberg stood on the convention stage and urged voters to back Clinton, the ''sane, competent person.'' Several prominent Republicans, including the two former presidents Bush and 2012 GOP nominee Mitt Romney, have not endorsed Trump.