Clearly, House of Representatives Speaker Nancy Pelosi smells blood in the water. Otherwise, she would not have launched an impeachment inquiry against President Donald Trump.

The question now is whether House Democrats circling to take a political bite out of Trump will attempt to ignore a potentially worse scandal.

For months, Pelosi, D-Calif., has resisted calls from the left wing of her party to begin impeachment proceedings against Trump. This week, she apparently sensed controversy regarding U.S. relations with Ukraine might provide an opening against the president. House Democrats plan to investigate contacts between Trump and Ukrainian President Volodymyr Zelenskiy. They are focusing on a July 25 phone conversation in which Trump discussed a situation involving former Vice President Joe Biden, currently the front-runner for the Democratic nomination for president.

In his conversation with Zelenskiy, Trump referenced an event in March 2016, when Biden, representing the United States, traveled to Ukraine and told the country’s leaders then they would not receive $1 billion in promised U.S. aid unless the country’s chief prosecutor was fired.

Biden admits doing just that. But he and other Democrats insist the Ukrainian prosecutor was corrupt. It happens that the prosecutor was looking into allegations of corruption involving Biden’s son, Hunter. Biden’s action brought that probe to an end.

Trump’s phone call was an attempt to get the Ukrainian investigation involving both Bidens resumed.

Pelosi’s party controls the House, so Democrats are in the driver’s seat on how the impeachment inquiry will proceed. But they have opened a Pandora’s box. Any attempt to cover up Biden’s role in the affair will be seen through by voters. If the House investigation is to be viewed as anything other than what Trump says it is — a witch hunt — lawmakers cannot give Biden a free ride.