(CNN) The US has grown more divided along partisan lines over the last two decades and past polling suggests the current impeachment inquiry into President Donald Trump is likely to only exacerbate those growing divisions.

Polling shows that the US is as divided on party lines as it's ever been -- and the start of that trend can be tracked back to the last impeachment crisis in the late 1990's involving then-President Bill Clinton. But that impeachment, and the impeachment inquiry into President Richard Nixon, took place at a time when the parties were far closer together.

Last month, House Speaker Nancy Pelosi opened an impeachment inquiry centering around Trump's phone call with Ukrainian President Volodymyr Zelensky after a whistleblower filed a complaint about the call. A transcript of the conversation released by the White House shows Trump repeatedly pushed Zelensky to investigate former Vice President Joe Biden and his son, Hunter. There is no evidence of wrongdoing by either Joe or Hunter Biden.

It's the first impeachment inquiry since Clinton was impeached by the House and then acquitted by the Senate, but the backdrop of Clinton's impeachment was a country that was far less divided on partisan lines than it is now. America is about as divided on party lines as it has ever been and the view going forward isn't rosy. Only 6% of Americans think the divisions will decrease, and the divisions aren't just skin-deep. Almost three-quarters said that Republican and Democratic voters not only disagree on plans and policies, but they disagree on even basic facts (including 77% of Republicans and 72% of Democrats), according to the recent Pew poll.

In 1997, about a year before Clinton was impeached, 22% said there was a great deal of difference between the parties. Now, over half of Americans believe there is a big difference between what the Democratic and Republican parties stand for, according to a Pew Research Center survey.

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