The Senate is the big prize. Until recently, Democrats felt confident they could get the four seats they needed to take back control if [Hillary] Clinton is in the White House and Vice President Tim Kaine held the tie-breaking vote.

Mitt Romney got 59 percent of the white vote in 2012, considered by many to be a high-water mark with this demographic group. Can [Donald] Trump win a higher share of white voters than Romney and get more of them to turn out?

Well, we had a bunch of primaries and caucuses on the Democratic side. Bernie Sanders won the Nebraska and Kansas caucuses. That keeps his campaign alive. But Hillary Clinton won Louisiana, which was the big prize of the night, so she ended up winning more delegates than he did yesterday.

Republican candidates have won whites with college degrees in every presidential election since polling began.

Hillary Clinton is also not a very exciting, inspiring candidate to a lot of the left-leaning Democratic base, especially in Iowa.

In 2012, Hispanics were 10 percent of the electorate, underperforming their share of the voting-age population. Mitt Romney got 21 percent of their vote, and [Donald] Trump has been polling much lower than that.

White voters were 72 percent of the electorate in 2012, and their share of the population has shrunk a couple points since then. [Donald] Trump has had trouble winning certain segments of the white vote, such as suburban women and college-educated voters.