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By a decisive margin, Democrats attending Iowa's presidential caucuses Monday said they preferred a nominee who is more likely to win the general election in November than a candidate who shares their positions on key issues, according to data from the NBC News entrance poll.

When asked to choose, about two-thirds of voters participating in the caucuses — 61 percent — said they would rather see the Democratic Party nominate a candidate who "can beat Donald Trump," while just one-third — 37 percent — want a nominee who "agrees with you on major issues."

Sen. Bernie Sanders, I-Vt., who came within a hairsbreadth of winning the Hawkeye State's Democratic caucuses in 2016, was holding on to the support of just over half of those who caucused for him four years ago, according to the numbers provided by the NBC News Entrance Poll Desk.

The rest of Sanders' 2016 voters were divided among Sen. Elizabeth Warren of Massachusetts; former Mayor Pete Buttigieg of South Bend, Indiana; and former Vice President Joe Biden.

The data pointed to a generational divide as voters under 30 said they supported Sanders while voters ages 65 and over said they favored Biden.

The entrance poll found Sanders capturing the support of about half of caucusgoers ages 17 to 29 — 48 percent — with Buttigieg, Warren and Biden trailing well behind.

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But among seniors, the data told a very different story: Biden was supported by 33 percent of participants ages 65 and over, followed by Buttigieg, Warren and Sanders.

Big decisions

Monday's caucuses saw an uptick in late-deciding Democrats from 2016. About one-third of those participating said they waited until the last few days to make up their minds about whom to support, according to the numbers. That marks a significant jump from four years ago, when just 16 percent of caucusgoers said they waited until this late to decide.

Meanwhile, more than 1 in 10 caucusgoers said they waited until Monday to decide whom to support. Biden and Buttigieg were the favorites among that group of voters, both attracting more than 1 in 5 of them.

Those voters were particularly concerned with picking a candidate who would take back the White House in November, with most of them — 70 percent — saying nominating a candidate who can defeat Trump was more important to them than choosing a candidate with whom they agreed on key issues.

The issues

Health care led the list of issues that mattered most to Iowa Democrats participating in the caucuses, with about 4 in 10 (42 percent) selecting it as the most important public policy matter on their minds when they decided whom to support. Three other issues — climate change, income inequality and foreign policy — all trailed far behind health care.

Ideological divides

Self-described liberals made up nearly 7 in 10 of those participating in the caucuses Monday, according to the data. That is about the same as four years ago but a big leap from the previous contested Democratic caucuses in 2008, when liberals made up just 54 percent of Democrats who showed up.

Sanders was the favorite of voters who called themselves either "very" or "somewhat" liberal, followed by Warren and Buttigieg.

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But among caucusgoers who identified as moderate or conservative Democrats, Biden and Buttigieg were even at 25 percent.

'First-timers'

The data showed a big dip in first-time participants, with just about a third of caucusgoers fitting that description. That's lower than in 2016, when first-timers made up 44 percent of caucus participants.

Among first-time Democratic caucusgoers, Sanders and Buttigieg were the clear favorites. Nearly 3 in 10 of the first-timers (31 percent) said they backed the Vermont senator, and a quarter (25 percent) said their top pick was the former mayor. Warren (14 percent) and Biden (eight percent) trailed far behind.

This year's level of new participants is well shy of that in 2008, when a whopping 57 percent of Democrats said they had never caucused before.