D candidates have won the popular vote in the last few elections, and Harris is ahead in the popular vote now. So this should be effectively a question of whether she will win the electoral vote, which should be in the 40-60 range of likelihood.

@CraigDemel Not quite. Harris is a favorite to win the popular vote, but not a shoo-in as you claim. She's ahead by 2.8 points on 538's average, and the national polling average has been off by an average of 2 points in Democrats' favor in the last 3 presidential cycles, D+3 in the Trump era, and 2.3 points in some direction historically

If the race tightens by one point, and the polls have underestimated Trump again by like ~2 points, she'll lose the popular vote too. Which is why e.g Nate Silver currently only has her as a ~63% favorite to win the popular vote. Then the rest of the math is straightforward