Cory Booker’s early fundraising numbers are well behind those posted by other major candidates in the race to challenge Donald Trump.

The New Jersey senator, who campaigned on Sunday in New Hampshire, said he raised more than $5m in the two months since he entered the 2020 primary, and has more than $6.1m cash on hand.

Booker announced the figure in an email to supporters. The sum puts him near the back of the pack in fundraising with roughly 10 months to go before the start of primary voting. Of those candidates that have announced their figures, only the entrepreneur and rank outsider Andrew Yang announced raising less.

Senator Kamala Harris of California raised $12m in the first three months of the year while Pete Buttigieg, the mayor of South Bend, Indiana, who has seen a bump in opinion polls, announced this week he had raised $7m.

Beto O’Rourke, a former congressman from Texas, raised $6.1m in his first 24 hours and $9.4m in his first 18 days, his campaign has said. Senator Bernie Sanders raised $5.9m in the day after announcing his candidacy, and later disclosed he had raised $10m in a week.

Money is important but it is definitely not going to be the barometer with which people make their decisions Cory Booker

Fundraising has become an early way to prove to donors and potential supporters that a candidate is viable. Donations to Booker averaged about $34, with 82% of the donors new supporters, spokeswoman Sabrina Singh said on Twitter.

Candidates are required by law to report all campaign donations, and cannot accept more than $2,800 from a single donor during the primary race.

The Massachusetts senator Elizabeth Warren has said her campaign will not hold any formal fundraising events and will instead rely solely on “small-dollar” donations or contributions collected online.

Booker insisted on Sunday he felt “incredible” about his fundraising haul.

“Money is important but it is definitely not going to be the barometer with which people make their decisions over who’s going to be the next president of the United States,” he said. “And I’m happy that we have the resources we need to be in this race.”

On the policy front, Booker promoted a program known as baby bonds which calls for newborns to get a savings account. The government would contribute up to $2,000 annually until the child is 18. The amount would depend on parents’ income.

Booker’s campaign says it is expected that one in 10 kids in New Hampshire would receive the full $2,000 annually. He said the plan would let kids use the fund to get training, go to college, start a business or buy a home. Booker said the idea was to “create a fair playing field where everybody has a stake in this economy”.

Elsewhere on Sunday, Buttigieg defended his experience, saying he was not someone who has “been marinating in Washington” for a long time. Asked on NBC’s Meet the Press about his qualifications, he said he would “stack up my experience against anybody”, though he acknowledged “it’s not as traditional”.

The Democratic field is full of senators, members of the House and governors. Buttigieg said “being a mayor of a city of any size means that you have to deal with the kinds of issues that really hit Americans”.

He would not confirm that he will formally announce his candidacy next Sunday in South Bend but said: “The kind of thing we’re going to announce is the kind of thing you only get to announce once.”

Buttigieg was also campaigning in New Hampshire. The Colorado senator Michael Bennet was there too, days after he made public a prostate cancer diagnosis.

Bennet said he was not dwelling on the diagnosis and spoke to voters about healthcare and partisan divides in Washington. He told CNN’s State of the Union he hopes to announce a run for president “as soon as I can”, depending on his health.

“I have got to go through a procedure at the beginning of the upcoming recess,” Bennet said. “That starts later this week. And then it’s going to be a couple of weeks for recovery. But I would like to get on with this.” He added that he was “looking forward to running in 2020”.

“This obviously was unexpected,” Bennet said. “But we caught it early. It’s something I think we’re going to be able to treat. And I don’t think it should keep me off the trail.”