Lynn Vavreck for NYT’s The UpShot:
These descriptive differences are negligible compared with differences relating to politics and policy. The YouGov data reveal that undecided voters are much less likely to have positions on issues driving the campaign. On the question of whether the United States should build a wall on its border with Mexico, a position central to Mr. Trump’s campaign for over a year, 28 percent of undecided voters are not sure whether they support or oppose this idea. That’s in contrast to only 7 percent of Mr. Trump’s committed voters (and 11 percent of Mrs. Clinton’s).
Similarly, undecided voters are roughly twice as likely to be unsure whether the minimum wage should be raised or whether college should be free.
The RAND data underscore this indecision. Seventeen percent of undecided registered voters are not sure whether they have a favorable or unfavorable view of the Republican Party (relative to 3 percent of Trump supporters and 13 percent of Clinton supporters). Similarly, 17 percent are unsure about their rating of the Democratic Party. Even on favorability ratings of the president, undecided voters are three times as likely as supporters of either major party candidate to say they “don’t know” how to rate him.