Poll shows Biden with 13-point lead over Trump in Florida.

With just over 100 days until Election Day, a new Florida poll shows Democrat Joe Biden significantly ahead of President Donald Trump.

The Quinnipiac University Poll released Thursday showed the former vice president 13 percentage points ahead of the president.

Biden has the support of 51% of Florida voters, with 38% choosing Trump.

The Quinnipiac Poll is the latest in a series of surveys that show Biden ahead in a state Trump won in 2016 and is vital to his for reelection. The RealClearPolitics average of six Florida polls released in July has Biden leading by 7 percentage points.

Of the 18 Florida polls since April 1, Biden has led in 17 and was tied with Trump in two.

The Biden lead in the Quinnipiac Poll is his largest so far. “The president doesn’t escape the shifting moods and concerns of voters in Florida. His sagging numbers are a gut punch from one of the key states he keenly hopes to win,” Quinnipiac polling analyst Tim Malloy said in a written statement.

The previous Quinnipiac Poll, released April 22, found 46% of registered voters favoring Biden to 42% for Trump.

Florida is the largest state that could go either way in the presidential election, awarding 29 of the 270 electoral votes needed to win the presidency. The state consistently produces close statewide elections, with key contests often decided by small margins.

In 2016, Trump won 49% of the vote statewide to Democrat Hillary Clinton’s 47.8%.

On July 23, 2016, the RealClearPolitics average had Trump ahead of Clinton by four-tenths of 1 percentage point.

Besides the overall result, another bad sign for the president: Polling usually shows him running much better in Florida than nationally.

But Thursday’s Florida poll results are almost the same as Quinnipiac’s most recent national poll, released July 15. The national poll showed registered voters backing Biden over Trump 52% to 37%.

The RealClearPolitcs average of eight national polls released this month has Biden leading by 9 percentage points.

The poll shows both voters need to pay attention to people 65 and older — the group most likely to actually turn out and vote.

Among older voters, Biden he leads 49% to 46%, a 3-point advantage. A potential trouble sign for Biden: In April, he had a greater lead among voters 65 and older, 52% to 42%, a 10-point advantage.

A potential trouble sign for Trump: in July 2016, he was 10 points ahead of Hillary Clinton among Florida’s 65 and older voters.

Quinnipiac surveyed 924 Florida registered voters. Closer to Election Day, pollsters switch to likely voters in an attempt to better focus on people expected to vote.

The survey, conducted from July 16-20 with live callers to landlines and cellphones, has a margin of error of plus or minus 3 percentage points.

The sample size for smaller groups, such as Democrats, Republicans and independents, is smaller and the margin of error is higher.

Pollster ratings from FiveThirtyEight.com give Quinnipiac a B plus for its data gathering and accuracy.