Trump's claim about Hillary Clinton in Bosnia may or may not be accurate, but the fact is that his credibility is long gone. Anyone who has paid close attention knows that he often makes a claim one day and then says the opposite a week or a month later. It's impossible to know what Trump will say or what he will support from one day to the next. He has less credibility than any presidential candidate in my lifetime.
Donald Trump's campaign for the Presidency has been full of gaffes - it seems that "The Donald" doesn't have a filter at all. He recently hit a new low when he claimed that Hillary Clinton, the presumptive Democratic Party nominee, had made up a story about sniper fire in Bosnia. If Trump continues to make such claims in order to smear his rival, the number of people who believe him will start to shrink.
Donald Trump has lost all credibility. He recently stated Clinton made up a story about Bosnian sniper fire. However, he has consistently lied and switched positions so frequently, it is hard to believe anything he has to say. He recently indicated support for gun control, only to take it back a couple of days later after meeting with the NRA.
Donald Trump has not lost all credibility with many in the electorate. The story Trump told about Hillary Clinton lying about taking sniper fire in Bosnia is true. Hillary really did lie about the incident in Bosnia while campaigning for the Democratic Party's presidential nomination in 2008. Therefore, Trump calling Clinton dishonest for lying about this story does not hurt his credibility.