You asked what strategy has been successful. In the campaign mode, I've been using my stamina in the first 10 rounds or so to pile up HQs and capital, which I cash in for endorsements. Usually piling on two or three endorsements is enough to throw a 40-50 states in my direction, even if only marginally. I then hit the big states (CA, PA, IL, TX, FL, NY) for fund raising and begin rolling out ads and speeches. I tend to make a lot of speeches, sometimes two in a state in one visit: slamming my opponent in one, pimping my own position in another.
It's worked well in campaign mode: As Bill Clinton, I walloped the first five campaign opponents, and beat Nixon, though he was leading up until the end -- he outspent me almost 3 to 1! I won it by rolling through the midwest repeatedly giving speech after speech after speech in the last four weeks, and built up enough mindshare that the in-contestation states broke my way. It was fairly dramatic.
Can't get past TR yet, though. But I shall!