Democratic candidate for president, former Vice President Joe Biden makes remarks about the DNI Whistleblower Report as well as President Trumps ongoing abuse of power at the Hotel DuPont on September 24, 2019 in Wilmington, Delaware.

2020 Democratic White House hopefuls have drilled into foreign policy as U.S. tensions with Iran bubble, and a new poll suggests more primary voters put their faith in Joe Biden to navigate the crisis.

About a third, or 32%, of Democratic primary voters most trust the former vice president to handle foreign relations, according to a Morning Consult survey released Monday night. Another 20% of respondents have the most confidence in Sen. Bernie Sanders, I-Vt., to address the topic.

Twelve percent say they don't know whom they trust to tackle foreign policy, while 11% put their faith most in Sen. Elizabeth Warren, D-Mass. Former New York City Mayor Michael Bloomberg and former South Bend Mayor Pete Buttigieg tied as the most trusted candidate, among 6% of respondents.

Foreign policy, which generally got less attention than issues such as health care, climate change and immigration during the first year of the Democratic primary, has jumped to the top of candidates' minds following the U.S. killing of Iran's top general, Qasem Soleimani, earlier this month. Democrats who aim to challenge President Donald Trump have warned about a spiking risk of war in the Middle East following Iranian strikes on U.S. targets in Iraq and the White House's new sanctions on Tehran.

The presidential hopefuls will likely stress their foreign policy credentials again at Tuesday night's primary debate in Des Moines, Iowa. The candidates will take the stage together for the final time before the state's caucuses, the first nominating contest of the year, on Feb. 3.

Polls still broadly show that voters consider health care and climate change the two most important issues in the race. On health care, 29% of respondents to the poll trust Sanders the most, followed by Biden at 21%. Meanwhile, 24% of voters have the most confidence in Sanders to handle climate change, while 22% say the same about Biden.

Since Soleimani's killing, Biden and Sanders in particular have tried to leverage their foreign policy credentials for support. The former vice president has touted his eight years in the Obama administration and more than three decades in the Senate, casting himself as a steadier, more experienced hand than Trump on the world stage.

Sanders has highlighted his efforts to keep the U.S. out of war — including his 2002 House vote against authorizing military force in Iraq. The senator has repeatedly criticized Biden for supporting the 2003 Iraq invasion, which Sanders recently called "the most dangerous foreign policy blunder in the modern history of this country."

Polling also suggests Iowa voters have paid more attention to foreign policy in the weeks before the caucuses. A Monmouth University poll released Wednesday found 16% of likely caucus participants list foreign policy as one of their two most important issues in deciding which candidate to support — up from 6% in an August poll.

The polling outfit suggested Iran tensions drove the increased focus — and that the issue could give Biden a bump in support.

"Recent events in the Middle East seem to have resulted in an uptick in foreign policy concerns among Democratic caucusgoers. It's still a small number, but it could be helping Biden on the margins," said Patrick Murray, director of the Monmouth University Polling Institute.

The Morning Consult poll, taken from Jan. 10-12, surveyed 801 Democratic primary voters and has a margin of error of plus-or-minus 3 percentage points.

The Monmouth University poll, taken from Jan. 9-12, surveyed 405 Iowa voters likely to attend the Democratic caucuses, and has a margin of error of plus-or-minus 4.9 percentage points.

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