If there is a smoking gun in the case of former Vice President Joe Biden’s involvement with Ukraine, it is being held by his son, Hunter.

Democrats in Congress and many in the media insist neither Biden did anything wrong in relation to Hunter’s membership on the board of Burisma Holdings, a Ukrainian natural gas company. On the other hand, they insist President Donald Trump is guilty of an impeachable offense for asking Ukrainian officials to investigate both Bidens.

At the heart of it all is the relationship between Hunter Biden and Burisma.

In 2014, while his father was vice president, Hunter Biden accepted an offer from Burisma for a position on its board, paying him as much as $50,000 a year. At that time, a Ukrainian prosecutor was investigating corruption that occurred at Burisma before Biden joined the firm.

In 2016, then-Vice President Joe Biden traveled to Ukraine and told officials there that $1 billion in U.S. aid would be withheld until that prosecutor was fired. He was.

Hunter Biden’s habit of capitalizing on his father’s position had been criticized previously. Knowing that, and understanding there would be questions about him using $1 billion in U.S. aid to pressure Ukrainian officials, why didn’t Biden ask his boss, then-President Barack Obama, to have someone else handle getting the prosecutor fired?

And if Hunter Biden’s relationship with Burisma was so innocent, why did he resign from the company’s board in April, after his father became a candidate for president? He did so because he believed the issue would hurt his father politically.

Again, did both Bidens worry that there was enough smoke rising from the Burisma connection that an investigation of it would uncover political fire?

Why are Democrats in Congress so intent on diverting attention from that issue? That alone ought to prompt thoughtful Americans to insist that the matter be investigated.