WASHINGTON — It's a proven political strategy: Underpromise and overdeliver.President Joe Biden, in his first three days in office, has painted a bleak picture of the country's immediate future, warning Americans that it will take months, not weeks, to reorient a nation facing a historic convergence of crises.The dire language is meant as a call to action, but it's also a deliberate effort to temper expectations. In addition, it is an explicit rejection of President Donald Trump’s tack of talking down the coronavirus pandemic and its economic toll.