Hillary Clinton and Donald Trump lead narrowly just two days before the Iowa caucuses in the final Des Moines Register/Bloomberg poll, considered the "gold standard" of Iowa polling.

But Clinton's 3-point lead over Vermont Sen. Bernie Sanders is within the margin of error.

Trump leads Texas Sen. Ted Cruz by 5 points, but pollster J. Ann Selzer noted that if evangelicals turn out in similar percentages to years past, Trump's lead shrinks to 1, though he still leads.

What's more, Trump appears to have very little room for growth. While he gets 28 percent for first place overall, just 7 percent say he's their second choice. Cruz, on the other hand, gets 23 percent overall, and an additional 17 percent say he's their second choice.

It could also be interpreted as good news for someone like Florida Sen. Marco Rubio. He comes in third currently with 15 percent, but he pops in the second-choice question. He leads as the top second-choice pick with 20 percent. But Des Moines Register political reporter Jennifer Jacobs pointed out that Rubio's support declined on each day of polling — not a good sign.

There is, however, good reason for Trump's lead in this poll. He beat his rivals on several leadership questions and, notably:

-- 35 percent said he can win general election, and

-- 50 percent said he's the candidate other countries would most fear

The GOP race is still very fluid with 45 percent saying they are persuadable. All that points to a very close caucus night on both sides with a lot more change possible for Republicans.

On the Democratic side, there are two good signs for Clinton:

-- One, 83 percent of Clinton supporters say their minds are made up, while 69 percent of Sanders supporters say so;

-- Two, as compared to 2008, there are fewer first-time caucusgoers. Just 34 percent in this poll said this would be their first Democratic caucus, as compared to 60 percent who said so in 2008.

Still, as noted above, the Democratic race is a margin-of-error race. And there are a couple of reasons for that:

-- Sanders' message has been resonating. That is evidenced by his 51-to-37 percent lead on the question of who most cares about people like you;

-- And there's a big generational divide. Sanders has whopping leads with voters under 45, including women under 45, while Clinton leads big with older women.

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