WASHINGTON D.C.- President Barack Obama is casting his seven divisive years as a time of positive change, implicitly asking voters to replace him with a Democrat who would continue his hard-won policies on health care, climate change and Iran.
    
Obama used his final State of the Union address to summon an affirmative vision of his administration and for the future. He rebutted critics, naysayers and the GOP White House hopefuls, but also acknowledged his own failure to transform the country's bitter politics and unite the nation.
    
With a year left in office, he presented that task as more urgent than ever and pleaded with voters to turn away from harsh voices and come together.
    
He said, "Our public life withers when only the most extreme voices get attention."