Bernie Sanders speaks to supporters in Dover, N.H. Jacob Pramuk | CNBC

ROCHESTER, N.H. — Waiting in a line wrapped around a city block, some shielded from biting wind by hats with "BERNIE" written on them, Bernie Sanders supporters reflected on how much their candidate's movement has changed. Entering New Hampshire's first-in-the-nation primary in 2016, the senator from Vermont had come just short of defeating former secretary of State and Sen. Hillary Clinton in Iowa's Democratic caucuses. While Sanders' Hawkeye State showing predicted the surprise strength of his 2016 primary bid, he really announced his presence when he beat Clinton by more than 20 percentage points in New Hampshire. Voters who backed Sanders in the Granite State four years ago say his crowds have grown: 1,100 people showed up to his remarks here Saturday, while a few dozen others turned away at the door waited in the cold as the event started. On Monday night, hours before the primary, over 7,500 people showed up for a rally, according to the campaign. Voters note that his campaign has become more sophisticated. And they insist that Sanders' core beliefs have grown more popular — which they say invalidates arguments from rivals that he would not beat President Donald Trump in November. "The unelectability argument no longer holds," 52-year-old X-ray technician and Sanders volunteer Dean Kandilakis said as he waited for Sanders to speak at the Rochester Opera House. "How is he not electable?"

The unelectability argument no longer holds. How is he not electable? Dean Kandilakis X-ray technician and Sanders volunteer

Sanders' rivals — and some voters who back them — have used a handful of criticisms of the senator as he led every poll ahead of Tuesday's New Hampshire primary. Former Vice President Joe Biden and Sen. Amy Klobuchar argue his views will damage congressional candidates in swing districts. Several competitors warn his signature "Medicare for All" health proposal would cost too much and take away private plans that many voters like. Sanders enters Tuesday's primary with the money and national and state polling numbers befitting a front-runner for the Democratic nomination in an 11-person race. Polls of the Granite State suggest he leads Pete Buttigieg, the former South Bend, Indiana, mayor who has taken a drubbing from his rivals after leaving Iowa with the most pledged national delegates in the field. In the final days before the primary, the Vermont senator has credited his neighboring state with helping to fuel his rise to a national force in 2016. Sanders hopes New Hampshire can propel him again Tuesday as he looks to seize control of the race before it turns to larger, more diverse states where Buttigieg has struggled to gain polling traction. "Four years ago when I was here campaigning, many of the ideas that we talking about — raising the minimum wage to a living wage of 15 bucks an hour — those ideas then were considered radical," Sanders said at a New Hampshire Democratic Party dinner on Saturday, where each presidential hopeful spoke to a cheering section of supporters at SNHU Arena in Manchester. "You know what? They're not radical today," he said, while also highlighting his plans to make public college tuition free, cancel student debt and implement a single-payer health-care system.

The Bernie Sanders section cheers at a New Hampshire Democratic Party dinner on Feb. 8, 2020. Jacob Pramuk | CNBC

Sanders led Buttigieg by about 7 percentage points in New Hampshire entering primary day, according to an average of recent polls. Klobuchar, fresh off a well received performance in Friday's Democratic debate, was statistically tied with Warren and Biden for third. Polls released ahead of the primary showed a fluid race. Sanders led Buttigieg by about 4 points in an NBC News/Marist poll of New Hampshire voters released Friday before the Democratic debate. Other surveys since have found larger advantages for Sanders. Voters do not always align with the neat ideological "lanes" described in coverage. Sam Kelley, an undecided voter who attended Sanders' Rochester event on Saturday, said she was choosing among Sanders, Klobuchar and Buttigieg. The latter two have proposed more modest policy changes than Sanders. Kelley, who works in the city of Rochester's finance office, said she was weighing which of those presidential hopefuls had the best chance to beat Trump.

Biden, the national polling leader throughout most of the race, finished a disappointing fourth in Iowa and predicted more trouble ahead. Sanders, who was the first choice of a plurality of Iowa caucus voters, finished just behind Buttigieg in national delegates from the state. Polls show a potentially close race in the Feb. 22 Nevada caucus and contenders angle to win South Carolina's primary on Feb. 29 and the March 3 Super Tuesday prizes of California and Texas. Struggles for Biden — who has generally fared best among the candidates with voters of color — offer an opportunity for Sanders. Former New York Mayor Mike Bloomberg, who has climbed in national polls as he piles tens of millions of dollars into Super Tuesday states, has complicated any path the front-runners have to the nomination.

Sanders hits Trump on the economy

Sanders increased his criticism of his competitors in the final days before the New Hampshire primary. On Monday, he told supporters that Buttigieg and Biden have "dozens and dozens of billionaires" contributing to their campaigns, while "we don't have any." Like some of his rivals, Sanders has started to preview the arguments he could use against Trump in a general election. The senator contended Friday morning that the benefits of a strong U.S. economy and near 50-year low unemployment — the core of the president's argument for reelection — have gone to the rich rather than the workers. "Last year in this 'booming' economy the average American worker in inflation-accounted-for dollars saw a 1% increase in his or her wages," Sanders said at an event held by St. Anselm College's New Hampshire Institute of Politics. "Why is that? How does it happen that year after year after year, people on top do phenomenally well, year after year after year, working class and middle class of this country struggle and 40 million people live in poverty?" Other Democrats have stressed the need to undercut Trump's economic arguments in November. During Saturday night remarks in Manchester, billionaire activist Tom Steyer said, "Donald Trump can win unless we kick his a-- on the economy." Trump touted the economy during a Manchester rally on Monday night in a direct challenge to the Democrats' messaging. New Hampshire had a 2.6% unemployment rate in December, among the lowest in the country. Some who live and work in Manchester, the state's largest city with about 112,000 people, expressed general satisfaction with the economy. Technology companies and universities have spread in a city once fueled by its textile industry.

Adam Coughlin works at the York.ie offices in Manchester, N.H. Jacob Pramuk | CNBC