(CNN) This weekend's new CNN/Des Moines Register/Mediacom poll shows former Vice President Joe Biden leading the pack with 24% and a close fight for second between Vermont Sen. Bernie Sanders at 16%, Massachusetts Sen. Elizabeth Warren at 15% and South Bend, Indiana, Mayor Pete Buttigieg at 14%. California Sen. Kamala Harris, at 7%, was the only other candidate to get above 2% in the poll.

But beyond the topline, here are some important factors to watch in Iowa.

Buttigieg and Warren show strength

In-person vs. virtual caucusgoers

This was our first poll in which we attempt to replicate a new rule in which 90% of delegates will be decided by in-person caucuses and 10% through virtual caucuses. Interestingly, our poll found that even though just 10% of delegates will be determined through virtual caucuses, 28% of likely caucusgoers say they will vote this way . If this divergence holds through the caucuses, it could mean that virtual caucusgoers will have their votes count for less.

Biden's age

A look at the data reveals multiple weaknesses for the frontrunner. One such potential weakness is that 46% of likely in-person caucusgoers think that a candidate over the age of 70 would be at a disadvantage against President Donald Trump. This even includes 29% of Biden's own supporters. This could be especially harmful for the now 76-year-old given that much of his sell to voters is his ability to beat Trump.

Warren's segmented support

This was arguably Warren's best poll of the entire campaign. She's only 9 points behind the leader. At 38%, she scored the best very favorable rating (a variable strongly correlated with vote choice) among in-person caucusgoers. But just like nationally, Warren's struggling to get on the board with more moderate voters. She gets only 5% of self-identified moderate in-person caucusgoers in our poll. If Warren's going to win in Iowa (and especially in other states where moderates make up a larger share of the vote ), she'll likely have to do better.

Sanders' divided base

Back in 2016, Sanders was the liberal and young voter alternative. He's not this year . Among the top five candidates in our poll, all but Biden do their best among in-person caucusgoers who call themselves either very liberal or somewhat liberal. All but Biden also do their best among those under 45 years old. This presents both opportunity and danger for these four candidates. If they can coalesce these groups, it could be golden for them. If they can't, Biden may be able to sneak out a win on the backs of moderate and older voters.

The 15% threshold