HAMPTON FALLS, N.H. (Reuters) - The simmering rivalry between progressives Bernie Sanders and Elizabeth Warren, presidential contenders with similar policies but sharply different styles, is headed for a showdown in New Hampshire.

FILE PHOTO: Democratic 2020 U.S. presidential candidate and U.S. Senator Bernie Sanders (I-VT) speaks at a campaign rally in Dover, New Hampshire, U.S. September 1, 2019. REUTERS/Brian Snyder/File Photo

The state’s Feb. 11 Democratic primary election is likely to decide which of the two neighboring U.S. senators, Sanders from Vermont or Warren from Massachusetts, emerges as the top liberal challenger to establishment front-runner Joe Biden in the 2020 race to pick a nominee to take on Republican President Donald Trump.

The two progressives, who campaigned in New Hampshire over the Labor Day holiday weekend and will return again later this week, are increasing their staffing and visits in the New England state that holds the second nominating contest in the Democratic race.

Recent opinion polls show Sanders running second and the steadily rising Warren third behind Biden in New Hampshire, where they are known quantities to the state’s big bloc of liberal voters. Exit polls in 2016 found 68% of those who cast a ballot in the Democratic primary considered themselves very or somewhat liberal.

That makes New Hampshire, a traditional proving ground that can make or break presidential contenders, ground zero for the inevitable Sanders vs. Warren conflict.

“It will be a real challenge moving forward for the one who doesn’t win, or finishes behind the other. It will have a damaging effect,” said Jim Demers, co-chairman of Barack Obama’s 2008 New Hampshire campaign, who has endorsed U.S. Senator Cory Booker of New Jersey in the race.

In 2016, Sanders won 60% of the primary vote in beating Hillary Clinton in the state during an unsuccessful run for the White House.

Given his strong performance, Sanders faces more pressure and bigger expectations than Warren this time around, said Kathy Sullivan, a former chairwoman of the state party who has not backed a candidate.

“Bernie needs to win here,” she said. “It doesn’t mean it’s over if he doesn’t, but it’s going to be much harder for him.”

The two candidates share similarities in ideology and have promised not to criticize each other, but they showed plenty of stylistic differences during their weekend visits to New Hampshire.

At a town hall meeting and a rally on Sunday, Sanders soberly reminded crowds he was attacked during the 2016 campaign for his “radical” ideas such as Medicare for All, free public college tuition and a higher federal minimum wage, all issues that have now moved into the Democratic mainstream.

“These are no longer radical ideas,” said Sanders, whose speeches were almost devoid of personal references.

At an outdoor house party in Hampton Falls on Monday, Warren laced her talk with personal details and jokes, drawing a link between the financial uncertainty of her childhood in Oklahoma and the impact it had on her populist economic policies.

“That’s why I’m in this fight,” she said, before taking selfies with members of the crowd in a driving rain.

‘BERNIE BEATS TRUMP’

Both Sanders, 77, and Warren, 70, addressed one of the biggest voter concerns about their candidacies: their ability to win over enough moderate and independent voters to beat Trump in November 2020 and recapture the White House.

Sanders repeatedly touted polls showing him beating Trump in a head-to-head matchup. Ben Cohen, a Sanders supporter and co-founder of the Vermont ice cream company Ben & Jerry’s, led the crowd in a chant of “Bernie Beats Trump!”

Warren was asked in Hampton Falls about concerns over her electability.

“I think what is going to carry us as Democrats is not playing it safe,” she said. “You have got to give people a reason to show up and vote, and that’s what I’m doing.”

There are differences in the two senators’ appeal. Some polls show Sanders doing better among young people, lower-income earners and people without a college degree. Those without a degree were 40% of the Democratic electorate in the state in 2016.

Dean Merchant, a writer from Stratham, said he backed Sanders in 2016 but thought it was time for a woman in the White House. He is considering Warren, as well as U.S. Representative Tulsi Gabbard of Hawaii and U.S. Senator Kamala Harris of California.

“I like Bernie, but he’s like Biden - he’s older now,” Merchant said. “At this stage I would like to see someone more vibrant, strong and forceful.”

Kevin Daley, an acupuncturist in Raymond, said he was backing Sanders but would be happy with Warren.

“She’s a brilliant person and she has been a good progressive. I just hope they don’t end up splitting the vote and we end up with Biden - that’s the danger,” said Daley.

Jeff Weaver, a senior adviser to Sanders, said the campaign has about 50 paid staff in the state and will hire more. New Hampshire is an important step toward the nomination, he said, “but I don’t think there is any one state that will make or break this campaign.”

The Warren campaign has five field offices in New Hampshire, with a sixth opening this week. It did not provide a number of paid staff in the state. Biden has 45 paid staff here, said Terry Shumaker, a Biden supporter who co-chaired Bill Clinton’s state campaigns.

Sanders and Warren will both be back this weekend at the state Democratic convention. Warren has been in the state on 17 days since January, and Sanders on 12, according to a candidate tracker at the NBC10 television station in Boston.

New Hampshire has a history of being kind to its neighbors, particularly those from Massachusetts, with past winners from the state including Republican Mitt Romney and Democrats John Kerry, Paul Tsongas and Michael Dukakis.

Arnie Arnesen, a liberal radio host and former New Hampshire state legislator, said she was like many voters in the state who have not chosen a candidate yet.

“I’m not feeling pressured to make a choice,” she said. “It is going to be very close with Elizabeth and Bernie coming out of here. Why choose now?”