Donald Trump and Hillary Clinton are leading the field in the final Iowa poll released before the caucuses.

On the Republican side in the latest Des Moines Register/Bloomberg Politics poll released Saturday evening, Trump came in with 28% support, up 6% from early January.

He’s followed in the Republican field by Texas Senator Ted Cruz with 23%, down 2% from early January, and Florida Senator Marco Rubio comes in third with 15%, up 3% from early January.

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Former neurosurgeon Ben Carson received 10% support and Kentucky Senator Rand Paul received 5%; all other Republican candidates received less than 5% support.

There are reasons for Trump to feel secure at the top: his supporters are the most confident among the top three candidates, with 71% saying they’ve decided, compared with 61% for Cruz and 47% for Rubio.

But there’s still some room for change. Rubio is climbing, and poll results show that he’s the top second choice pick of likely voters. And Cruz’s favorability rating has dropped by 11 points, to 65%. Trump’s biggest weaknesses are his support for eminent domain, which worried 60% of the respondents, and his previous support of abortion rights, which bothered 56% of respondents.

The Democratic side remained relatively stable from the early January poll, locked in a tight race within the margin of error for former Secretary of State Clinton and Vermont Senator Bernie Sanders. Clinton received 45% support in the new poll, up 3%, but Sanders received 42%, up 2%. Former Maryland governor Martin O’Malley dropped 1 percentage point down to 3%.

Although the race between Clinton and Sanders is tight, Clinton is wining among Democrats who said they will definitely caucus, whereas Sanders is winning among those who said they will probably caucus. And 83% of Clinton supporters said they have made up their minds. This could give Clinton an edge Monday night if Sanders can’t successfully boost turnout.

Iowa polls can be notoriously unreliable due to the complication of the caucus process and the unreliability of turnout. But J. Ann Selzer, who ran the poll, has conducted polling on the Iowa caucuses since 1988 and has an impressive track record.

According to Politico, Selzer was the only pollster to predict the order of the Democratic candidates in 2004, she accurately predicted the surge of first-time caucus attendees in 2008, and she was one of the only pollsters to see the rise of Rick Santorum in 2012.

This poll was conducted of 602 likely GOP caucusgoers and 602 likely Democratic caucusgoers from Jan. 26 to 29 and has a margin of error of +/- 4%.

Write to Tessa Berenson at tessa.berenson@time.com.