"People have to realize that what the media is doing here is pre-deciding an election," he told CNN's Alisyn Camerota on "New Day."
Fox Business announced last month that its January 14 debate would include the top six candidates based on the average of the five most recent national polls, as well as those who finish in the top five in Iowa or New Hampshire. Paul failed to meet that criteria.
But Paul argued because the most recent Bloomberg/Des Moines Register poll was conducted within the time frame allowed -- although not released until Wednesday -- he should be included in the top-tier debate.
"I have an important voice. What do you think the liberty movement, the liberty voters in the Republican Party are thinking now? That the Republican Party in league with the media networks is saying we're not going to let the liberty candidate on the stage," he said.
Paul said his exclusion from the main debate stage "disenfranchises the voters of Iowa or New Hampshire."
"So what it is, is about predefining the race? We have not had one vote yet and everybody is going crazy like Donald Trump has won the race already," he said.
Being relegated to the undercard debate communicates to voters that a candidate can't win, Paul said.
"If you're designated as someone who is not in contention, that is very disruptive to a campaign that is about three weeks out," he said. "There's only one debate tonight. Let's be honest about this."
The seven candidates expected to take the main stage at 9 p.m. are Donald Trump, Ben Carson, Ted Cruz, Marco Rubio, Chris Christie, Jeb Bush and John Kasich.
Both Paul and Carly Fiorina, who appeared on the main stage in last month's CNN debate, are relegated to the undercard round, along with Rick Santorum and Mike Huckabee, according to the Fox Business Network.