Washington (CNN) One septuagenarian New Yorker is a "5'4" mass of dead energy." The other septuagenarian New Yorker is a "carnival barking clown." Both are hoping to be president next year.

Neither man seemed wary of reducing their political sparring to insults about appearance, height or intelligence levels. It was a good indication of sourness to come as Trump eyes Bloomberg's rise in Democratic primary polls.

The incumbent initiated the insult volleys on Thursday morning, retweeting an altered image of Bloomberg that made him look shorter than a large stack of papers.

"Mini Mike Bloomberg is a LOSER who has money but can't debate and has zero presence, you will see," Trump wrote, comparing his potential rival to another onetime Republican presidential candidate, Jeb Bush, who he also once accused of lacking energy.

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