[...] Clinton will end the campaign still struggling to change the minds of millions of voters who don't think well of her, a glaring liability should the Democratic nominee move on to the White House. Democrats blame some of the current negative personal perceptions of Clinton on the hard-charging tactics she's used to try to discredit Trump, though they believe her sustained assault on Trump's character and temperament has been crucial. Party operatives also say Trump's personal attacks on Clinton have made it all but impossible for more positive messages to break through. "When you're under relentless assault from a reality TV star, it's hard to come out of that with anybody feeling good about anyone," said Bill Burton, a former Obama aide. [...] if Clinton is elected president, she won't have the luxury she had as secretary of state to stay away from the political fray — with Republicans in Washington in the opposition, and possibly Trump, too. Clinton has begun acknowledging the challenge that could await her in the White House, if she wins, centering her closing argument to voters on a call for unity after a bitter campaign. Some Democrats see the transition — the two month-plus stretch between the Nov.