In choosing to focus on his baby bonds proposal, Mr. Booker is seizing on an issue that has come to define the early primary race: inequality of wealth and income. While many other candidates paint broad agendas to combat the growing wealth gap, such as calls for “Medicare for all,” Mr. Booker’s baby bonds proposal is among the most complex and specific offered by a presidential candidate.

On the campaign trail, Mr. Booker touts a Columbia University study from January that concluded that baby bonds “would dramatically reduce racial wealth inequality.”

A broad rewriting of the social contract, Mr. Booker’s proposal calls for every child born in the United States to be given a $1,000 bonded savings account that is run through the Treasury Department. Each year, the federal government would contribute to the account on a tiered basis; those who come from a family of four making less than $25,100 a year would be given $2,000. The contributions would be lowered as families move up the income ladder, and any family of four making more than $125,751 would receive no contributions.

The proposal estimates that children from the nation’s poorest families would receive roughly $46,000 when they turned 18. But the money would carry restrictions; it could only be spent on “wealth-building” transactions like paying for college, buying a home or starting a small business.

Mr. Booker’s office estimates that the program would carry an annual price tag of about $60 billion, and would be paid for by restoring the estate tax rate to its 2009 levels, closing loopholes in the capital gains tax, and adding a surtax rate for estates worth at least $10 million and at least $50 million.

But just before Mr. Booker was about to delve into the more intricate details of his baby bonds proposal, he was interrupted by one of the home’s residents — Sadie, a golden lab.

“What are your questions,” he said, pausing his remarks to rub the dog behind the ears. “I am the leader in the Senate on animal issues.”