A new national poll contains warning signs for President Trump, showing former Vice President Joe Biden and a slew of other Democratic White House candidates leading the president in head-to-head matchups.

The Quinnipiac University public opinion survey, released Tuesday, also indicates a deterioration in Biden’s large lead over the rest of this historically enormous field of nearly two-dozen Democrats.

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But looking ahead to a hypothetical general election, the same survey shows Biden with a double-digit lead over the Republican president. According to the poll, Biden tops Trump 53-40 percent in a potential general election showdown for the presidency.

The survey shows Biden winning women voters by 26 percentage points, with men divided. And it indicates Biden with a 30-point lead among independent voters.

And it’s not just Biden – Sen. Bernie Sanders of Vermont leads Trump 51-42 percent, according to the poll. The survey shows Sen. Kamala Harris of California topping the president by 9 points, Sen. Elizabeth Warren of Massachusetts ahead of Trump by 7 points, and South Bend, Indiana Mayor Pete Buttigieg and Sen. Cory Booker of New Jersey each holding 5-point advantages.

“The head-to-head matchups give this heads up to President Donald Trump's team: Former Vice President Joseph Biden and other Democratic contenders would beat the president if the election were held today,” Quinnipiac University Poll assistant director Tim Malloy noted. "It's a long 17 months to Election Day, but Joe Biden is ahead by landslide proportions."

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But Malloy – pointing to the survey's new presidential approval rating – noted that “the Trump bump to 42 percent job approval is nothing to sniff at. It's one point shy of the best Quinnipiac University survey number ever for President Trump.”

Another potential warning sign for the president -- 70 percent of those polled said the country’s economy is “excellent” or “good,” but only 41 percent said the president deserved credit for the economy.

The poll’s release comes a week after a Quinnipiac University survey showed Biden with a 48-44 percent edge over Trump in reliably red Texas. Also last week, a Glengariff Group poll in the battleground state of Michigan indicated both Biden and Sanders topping Trump by 12 percentage points among likely voters.

Last month, a Quinnipiac survey in Pennsylvania showed Biden with an 11 percentage point lead over the president.

Michigan, Pennsylvania and Wisconsin are three Rust Belt states that made up the traditional Democratic "blue wall" in presidential elections that Trump narrowly captured in 2016, helping him to win the White House.

But first things first: Biden still has to win the Democratic presidential nomination.

And the new Quinnipiac survey suggests Biden’s large lead over his rivals is starting to shrink.

Biden stands at 30 percent support among Democrats and Democratic-leaning voters. That’s down from 35 percent in Quinnipiac’s May poll and 38 percent support in their late April survey.

Sanders stands at 19 percent, up 3 points from last month. Warren grabs 15 percent support, edging up 2 percentage points since last month. Buttigieg grabs 8 percent, with Harris at 7 percent and former Rep. Beto O’Rourke of Texas at 3 percent.

No other Democrat tops 1 percent in the poll, with 14 candidates registering less than 1 percent.

The Quinnipiac University Poll was conducted Jun 6-10, with 1,214 voters nationwide questioned by live telephone operators. The survey’s overall sampling error is plus or minus 3.5 percentage points.