Rep. Steny Hoyer has written this Roll Call oped (paid subscription required). A snippet:

That changed in 2004. To attract the widest possible audience, the Democratic Party scheduled its convention in late July, before the Summer Olympic Games began. In contrast, the Republican Party held its convention in the last week of August. The result was a six-week gap that forced Kerry to finance his campaign with public money while Bush continued to raise and spend money from private contributors.
Let me stress that I no more fault the Republican Party for scheduling its convention as late as it did than I do the Democratic Party for holding its convention in July. Each sought to avoid competing against the Olympics and with one another. But in my judgment, the timing of the conventions should not have had the effect of putting the candidate who was nominated first at a disadvantage.
Had this been a one-time problem, I would not feel moved to act. But it was not. Except in those years when the summer games are held south of the equator, the two major parties can expect to face the same challenges they did in 2004, forced to schedule their conventions around the “Summer Olympics as well as around one another.
To solve this problem, I have introduced H.R. 850, which would establish a uniform date for the release of public payments. H.R. 850 would designate the Friday of Labor Day weekend in a presidential election year as the day on which the party nominees receive public funds and must discontinue raising and spending private dollars.