LAS VEGAS — Just in case Vice President Joe Biden wants to shake up the first Democratic presidential debate, CNN has reserved a sixth podium for him at Tuesday night’s showdown in Las Vegas.

Biden is taking his time making a decision whether to run, and aides insist he won’t be a last-minute addition to the stage, where Hillary Rodham Clinton will face four rivals led by Vermont Sen. Bernie Sanders.

It would be a dream scenario for TV ratings.

Both Republican debates pulled in record viewers for Fox News and CNN.