Republicans have more cash on hand than Democrats for the presidential stretch run. Romney and allied Republican Party committees entered September with about $168.5 million and Obama and his committees had about $125.1 million, not counting debts, according to a Republican National Committee memo to supporters on Friday.

Under federal rules, commercial broadcasters must provide not only “reasonable access” to air time for all candidates for federal office, but “equal opportunity” to buy spots if an opponent has bought time at the station. Cable channels are not required to sell political ads unless they have sold time to one candidate. In that case, they must provide equal time to the opponent. Another reason viewers will be blitzed: any surplus money raised by PACs and federal candidates cannot be used after Election Day — unless its for a future campaign.