Well, credit is certainly due Trump for being consistent. He is, in effect, saying that he has no moral obligation to correct a lie being told about Obama. From there, it follows that lies he tells about Obama, likewise, are not subject to to any moral test, so at the same time he can, with facility, say that Obama has been a terrible President despite an overabundance of statistics to the contrary.
Furthermore, Trump has precedent to back him up when he blithely promises many things that he will accomplish, as President, without offering a single plan, for how it will be done, for evaluation by the electorate. Remember, for example, how Nixon offered us a secret plan to end the war in Viet Nam. The war dragged on throughout his entire term in in office and and only came to an end, under President Ford, a year after Nixon resigned the Presidency. For his pains in hoodwinking the American public, Nixon was reelected to a second term in 1972. For Trump, all his promises, even if not based on any reasonable expectation, can only assure him of being a two term President, considering the nature of the American electorate.