Four of the top six Democratic presidential campaigns spent heavily ahead of the Iowa caucuses, and they are now at a major disadvantage on the airwaves heading into next month’s crucial Super Tuesday contests.

While billionaire Michael Bloomberg is already spending about $156 million on TV and radio ads across the 14 states that weigh in on March 3, neither former Vice President Joe Biden nor former Mayor Pete Buttigieg had invested in a single Super Tuesday commercial as of Thursday night, according to ad tracker Kantar/CMAG.

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