National radio host Rush Limbaugh said Tuesday on "The Story with Martha MacCallum" that Joe Biden represents the Democrats' "best chance" to defeat President Trump in 2020. 

The former senator and vice president is set to announce his candidacy Thursday, becoming the 20th person to join the field. 

Limbaugh said Biden might be the strongest candidate to face Trump, but he still "doesn't have a chance" of preventing a second Trump term. 

He said the reason is that the media and the Democratic Party still do not understand the fundamental reasons why Trump won in 2016.  

"They still don't understand who Donald Trump is. They don't understand how he won. They don't understand how he's gonna win again in 2020. They don't understand the people who voted for him or why. They hold all of that in contempt," he said, referring to Biden and "crazy" Sen. Bernie Sanders as "brontosauruses from Jurassic Park." 

Limbaugh said Biden has delayed his entry into the race for so long that he now questions how bad the 76-year-old wants the job.

"I don't know how badly he really wants this and you have to really want this if you're gonna have any chance of winning it."

He said he believes Democrats and the media are becoming frustrated with Trump's staying power, especially after the conclusion of Special Counsel Robert Mueller's investigation. 

"They have thrown every weapon they have in their arsenal at Donald Trump, and nothing's worked. Things they've used over the years that have been readily available to get rid of and take out any Republican they want, they have bounced off of Trump," Limbaugh argued. 

Biden's candidacy is expected to launch Thursday with a video, followed by an appearance Monday in Pittsburgh. 

Watch the full discussion above.

Tucker: The Left Goes to 'Great Lengths' to Avoid Saying 'Christians' Attacked in Sri Lanka

Tucker: Mueller Probe 'Didn't Destroy Trump, But Did a Lot to Destroy This Country'