Why does the Public pay for political conventions?

Parties Weigh Convention Revamp

 Excerpts:

Driving the debate is a bipartisan push in Congress to cut significant public subsidies to the events. Eliminating the $36 million taxpayers chipped in to help stage this summer's two conventions would put all the more weight on already-hesitant donors.

... The Republicans' Tampa gathering cost taxpayers and private donors about $120 million. The Justice Department contributed $50 million for ramped-up security. Donors chipped in around $55 million, though raising that sum proved challenging, according to several participants.

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