WASHINGTON – It has been nearly three weeks since House Speaker Nancy Pelosi announced a formal impeachment inquiry on Sept. 24 into President Donald Trump's pressuring of the Ukrainian government to open an investigation into former Vice President Joe Biden and his son Hunter Biden.

House Democrats have escalated their inquiry, issuing subpoenas to several administration officials and associates of Trump's personal attorney Rudy Giuliani.

The White House has vowed not to cooperate with the impeachment inquiry, calling it a "partisan" probe.

Despite the clashes between the legislative and executive branches, public opinion polling has shown noticeable shifts in attitudes towards impeachment, though every single poll has asked about impeachment differently.

Partisan divides still persist in every poll, with Democrats and Republicans splitting on the issue. Independents, however, have slowly started to support impeachment or impeachment proceedings.

As of Oct. 10, an average of impeachment polls calculated by FiveThirtyEight, a polling analysis website, shows 49.3% of respondents supporting impeachment and 43.5% not supporting it.

Here is what the individual polls say about impeachment, separated by each question.

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Approve of the House opening an inquiry?

A poll conducted by NPR/Marist/PBS NewsHour from Oct. 3 to Oct. 8 shows 52% of adults support House Democrats starting an impeachment inquiry into Trump — 43% disapprove.

This is an increase from their earlier polling of the same question the night of Sept. 25, one day after Pelosi announced the impeachment inquiry. The poll showed Americans supported the opening of an inquiry at 49% to 46%.

Independents' views also appeared to have shifted in the early October poll: 54% of independents supported the opening of an inquiry, and 41% disapproved. In contrast, 50% disapproved and 44% approved in the Sept. 25 poll.

Polling by The Washington Post/Schar School released on Oct. 8 and conducted from Oct. 1-6 mirrored the finding: 58% of adults said they supported the opening of an inquiry and 38% opposed it.

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Voting to impeach?

A USA TODAY/Ipsos poll released on Oct. 3 and conducted from Oct. 1-2, just one week after the beginning of the inquiry, found 45% of Americans approved of a vote in the House to impeach Trump, and 38% disapproved of a vote. Forty-four percent of people in the same poll approved of the Senate voting to convict the president, and 35% did not.

In June, previous polling conducted for USA TODAY by Suffolk University found that only 31.8% of registered voters thought the House "should seriously consider impeaching President Trump," with 60.6% opposing it. That poll had been conducted prior to special counsel Robert Mueller's testimony before the House, and far before the emergence of details of Trump's Ukraine controversy.

Approve of impeachment and removal from office?

Fox News asks the question slightly differently in its poll. A Fox News poll conducted from Oct. 6-8 among registered voters shows 51% of voters supported Trump's impeachment and removal from office, 4% supported impeachment but not removal, and 40% opposed impeachment.

This result drew a rebuke from Trump, who tweeted on Oct. 10 to say "Whoever [Fox's] Pollster is, they suck."

When Fox had asked the same question in July of this year, 42% of voters supported impeachment and removal, 5% supported impeachment but not removal, and 45% opposed impeachment.

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Views on Trump and Ukraine?

The NBC/WSJ poll conducted from Oct. 4-6 asks about impeachment by asking adults what actions they think should be taken about Trump's dealings with Ukraine.

Adults were asked whether there was sufficient evidence to impeach and remove Trump, whether to hold an impeachment inquiry, whether there was insufficient evidence to hold an inquiry, or if they were not sure.

Twenty-four percent of adults said there was sufficient evidence to impeach and remove Trump, 31% said Congress should hold an inquiry, and 39% said there was insufficient evidence.

This meant a majority of Americans saw the Ukraine controversy as meriting action on impeachment.

When the NBC/WSJ poll had been conducted in July, adults were asked what Congress should do given discussion of impeachment and impeachment hearings.

At the time, 21% of Americans said there was sufficient evidence to begin impeachment hearings, 27% called for Congress to investigate to see if there was enough evidence for impeachment hearings in the future, and 50% said Congress should not hold impeachment hearings.