NEW YORK (Reuters) - Support for Democratic presidential front-runner Joe Biden ticked higher following reports that President Donald Trump pressured his Ukraine counterpart to investigate Biden, while Americans overall are less supportive of impeaching Trump than they were months ago, according to a Reuters/Ipsos opinion poll released on Tuesday.

Former U.S. Vice President and Democratic presidential hopeful Joe Biden makes a statement during an event in Wilmington, Delaware, U.S., September 24, 2019. REUTERS/Bastiaan Slabbers

In a sign that Biden’s supporters appear to be standing by their candidate, 20% of Democrats and independents said they would vote for him in statewide nominating contests that begin next year according to the Sept. 23-24 poll, up 1 percentage point from a similar poll that ran last week.

It also found that 37% of the American public thinks Trump should be impeached, down from 41% in a similar Reuters/Ipsos poll that ran earlier in September. This compares with 44% in a poll that ran in May, after the Trump administration released portions of the Mueller investigation on Russian meddling in the 2016 election.

The former vice president has been swept up in a political furor over reports that Trump discussed Biden in a July phone call with Ukrainian President Volodymyr Zelenskiy and asked him to investigate unsubstantiated charges that Biden improperly tried to halt a Ukrainian probe of a company with ties to his son Hunter.

The House of Representatives will launch a formal impeachment inquiry against Trump, after he confirmed the phone call at the center of the controversy on Tuesday and promised to release a transcript of the call.

Democrats have decried the call as an attempt by Trump to smear his top political rival, and the uproar has given Biden’s campaign a chance to portray it as evidence that the president see him as the most dangerous opponent among the 19 candidates seeking the party’s nomination to take on Trump in the November 2020 election.

But there is also a risk that Biden’s candidacy and perceptions of his electability could be hurt by the possibility of Trump’s repeated charges of corruption, strategists said.

“It could be distracting if the campaign becomes more about the allegations of corruption within the Biden family,” said Donald Green, a political science professor at Columbia University.

There has been no evidence to suggest so far that Biden used his position as vice president to help his son’s business in Ukraine, and he has said they never discussed the matter.

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Green also said it is a risky move if Democrats launch an impeachment inquiry so close to the 2020 election about a conversation that may be interpreted a number of ways.

“I don’t think the typical American knows much about the Ukraine or what President Trump was talking about,” Green said. “If this case is ambiguous, it’s something that can be tarred as a witch hunt.”

So far, most Americans say they are not closely following the growing scandal.

Only 17% of the public says they have heard “a great deal” about the news that Trump discussed Biden with the president of Ukraine. Another 31% said they knew “some” of the details and 52% said they know little, if anything, about the Ukraine news, the Sept. 23-24 poll showed.

Support for impeachment is higher among those adults who said they have been closely following the Ukraine news. Among those with a high level of familiarity, 5 out 10 said they think Trump should be impeached, while 4 in 10 said he should not.

The poll underscored the continued rise of U.S. Senator Elizabeth Warren.

She had 14% support among Democrats and independents, up 2 points from the previous poll and enough to surpass U.S. Senator Bernie Sanders as the second-most-popular choice for the Democratic nomination.

Sanders dropped by 4 points in the poll, receiving the support of 13% of Democrats and independents.

Biden, Sanders and Warren all narrowly lead Trump in hypothetical general election match-ups, but their lead was smaller in the latest poll than it was in June.

Biden led Trump by about 5 points, Warren led Trump by 2 points and Sanders led Trump by 1 point.

The Reuters/Ipsos poll was conducted online, in English, throughout the United States. It gathered responses from 1,005 U.S. adults and has a credibility interval, a measure of precision, of 4 percentage points.

Click here to see the full poll results: tmsnrt.rs/2kOCryy