Inside Biden’s orbit, there is a belief that the limited schedule is working. “We began the campaign in the lead and we’re still there. Why would we fix something that isn’t broken?” asks one Biden hand at the campaign’s Philadelphia headquarters. “Voters know Joe Biden, so we don’t have to introduce ourselves to voters.” Where his rivals have to subject themselves to voters’ constant probing, the thinking goes, Biden can go to voters he already knows to ask them for campaign contributions. In the last week alone, he’s picked up checks in Houston, Beaumont, Texas, Dallas, Miami, suburban Washington, D.C., and Chicago.

At least to this point, the scaled-back strategy appears to be paying off. Biden has strengthening his position as the leader of a jumbled pack of hopefuls, expanding his already considerable coalition and bedeviling rivals who had expected the front-runner’s support to collapse. An NBC News/ Wall Street Journal poll released Wednesday showed Biden had expanded his lead by five percentage points since July. Some 41% of Democrats in the same survey say they’d be comfortable with Biden atop the ticket, compared to 35% who say the same of Elizabeth Warren, his closest rival. Biden may be more durable than his detractors had expected.

In fact, Biden may be getting stronger as the campaign goes on. In April, Biden led in just one of the 19 subsets CNN pollsters released results for, and that was among self-identified moderates. He was tied in two others — non-white voters and those earning less than $50,000 a year. The September CNN survey found Biden in a stronger position, ahead in 18 of the 26 slices of the electorate. (Biden still lags Warren among women, liberals, those who are “extremely enthusiastic about the race,” all college graduates and white college graduates. He trails Sanders among Hispanics, voters under 50 and voters under 45.)