Harris support rises among some likely voters: POLL

Much of the work of election campaigning goes on beneath the radar, where campaigns fight furiously to identify and register potential supporters and ensure their participation. Identifying likely voters, as such, is a moving target -- but with absentee voting now beginning, an initial look reveals some intriguing patterns.

As previously reported , Kamala Harris leads Donald Trump by a slight 4 percentage points, 50-46%, among all adults and registered voters alike, and by 6 points, 52-46%, among likely voters in the latest ABC News/Ipsos poll. While those numbers are virtually identical, closer assessment shows movement to Harris in some groups when comparing all adults with likely voters -- notably, those younger than 40, younger women in particular and Black people.

This analysis, produced for ABC News by Langer Research Associates , finds that support for Harris goes from 54% of all adults younger than 40 to 64% of those identified as likely voters. Trump's support, meanwhile, drops from 42% of adults in this age group to 33% of those likely to vote.

That shift is driven largely by women: Harris' support increases from 60% of all women younger than 40 to 73% of those in this age group who are likely to vote. Trump sees a corresponding drop in support, from 35% among all women younger than 40 to 24% of those likely to vote.

Harris has 82% support among all Black people, rising to 93% among those who are likely voters. Trump, for his part, goes from 15% support among all Black people to 7% among those who are likely to vote. Harris also gains among liberals.

Countervailing movement in Trump's direction doesn't reach the level of statistical significance in any group. He has, for example, 52% support among all 50- to 64-year-olds (his best age group) and 56% among likely voters in this group. He goes from 85% to 88% among conservatives and from 52% to 54% among people who don't have a four-year college degree.

But it's not all about who receives more support in likely voter groups; it's also about the size of those groups. Harris, for example, leads Trump by 23 points, 60-37%, among likely voters with four-year degrees -- and, as such, benefits from the fact that this group makes up 45% of likely voters, vs. 35% of the general population.

Trump pushes back with his 10 point likely voter advantage among white people: they account for 61% of all adults but 71% of likely voters. He's also aided by a lower prevalence of adults younger than 40; they make up 36% of all adults vs. 25% of those identified as likely to vote.

All told, it's the combination of group sizes and preferences among groups that add up to keep the race a close one. Likely voters are defined here, in part, by people saying they are certain to vote. Motivating them actually to do so is what both campaigns are all about -- starting now.