Pundits are beginning to agree that Joe Biden’s campaign is in a death spiral.

“Biden’s campaign is running on fumes,” writes The Daily Beast‘s Sam Stein. “A candidate with all the trappings of a traditional frontrunner—the long résumé, party backing, relevant experience, and steady poll numbers—suddenly is on electoral life support.”

So what happened? Should Biden’s campaign crash and burn there will be much speculation over what went wrong. How did the frontrunner go from smooth sailing to the nomination to an epic disaster?

Well, I think the answer is already clear.

When you look at the Real Clear Politics tracking in the early states of Iowa and New Hampshire, you will notice a pattern: Biden starts losing support, or some other candidate starts to rise, around mid-September 2019.

Mid-September happens to be the same time the whistleblower complaint that launched Trump’s impeachment became public.

Looking at the graphs of Iowa and New Hampshire you see quite clearly how Biden’s candidacy was riding high, the unequivocal frontrunner, for months. Months! Then suddenly the race became competitive between Biden, Sanders, Warren, and eventually Buttigieg.

Biden has never regained that runaway frontrunner status since the Democrats started their bogus impeachment of Trump. And it’s quite easy to understand why.

Prior to the whistleblower complaint, Biden’s Ukraine conflict of interest was not on the public radar, but thanks to those revelations, videos of Biden admitting to a quid pro quo, and his son Hunter’s position at Burisma Holdings were being discussed and debated openly by media. For sure, the liberal media attempted to downplay the significance of Biden’s Ukraine problem, but Biden, who was seen as the sane and safe candidate, wasn’t so safe anymore. Even Biden’s cheerleaders on The View couldn’t deny it.

“Look, the Hunter Biden thing, there’s a legitimate issue there,” said Ana Navarro back in December. “I think that Joe Biden is going to have to answer that. I think that it doesn’t pass the smell test.”

“The Burisma thing is nepotism,” said Joy Behar. “And let’s just call it what it is. It’s just nepotism.”

Biden’s collapse would have happened much quicker if any of his rivals had called him out for his Ukraine/Burisma problems. For some reason, they didn’t, and it took the Iowa caucuses to show definitively that Democratic voters have real reservations about Biden’s Ukraine issues, and worried they’d be effectively used against him in November.

Democrats impeached Trump for suggesting there be an investigation into Biden and his son over Burisma, and yet their efforts to protect Biden may very well have doomed his campaign. The impeachment hearings became a very public platform for Republicans to air Biden’s dirty laundry for hours a day, and the public watched as even the Democrats’ own witnesses couldn’t deny the obvious about Hunter Biden and his father.

Democrats desperately tried to protect Joe Biden. They denied Republicans their own witnesses, and aggressively opposed any deals for more witnesses that would involve letting Hunter and/or Joe Biden testify. What they didn’t realize at the time was that when they thought they were protecting Joe Biden, they were actually hurting him.

Now impeachment is over, President Trump not only emerged unscathed but stronger than ever. Joe Biden, on the other hand, got shellacked in Iowa, and will likely get shellacked in New Hampshire as well. He still has the lead in Nevada and South Carolina, but it will be very difficult for him to overcome two major losses in a row.

Joe Biden’s frontrunner status was largely due to his perceived electability. By impeaching Trump, they revealed how risky nominating him would really be.