From Walter Shapiro writing for the Brennan Center:

This bleak political environment blinds us to a stunning reality about 2017 politics. Even beyond Ossoff, small donors have contributed a massive amount to 2017 House races. In Montana, with minimal help from the national Democratic Party, Rob Quist (a folk singer who had never held public office) corralled more than $3 million in just 10 weeks. Totals like this suggest that the $228 million that Bernie Sanders raised for the 2016 primaries was not an aberration.

The problem, of course, is that this torrent of small donor financing requires a national media spotlight on a specific race. In normal times, liberal donors in Beverly Hills or Brookline do not give much thought to the identity of the House member who represents Dunwoody, Georgia. But right now the battle in Georgia-6 is the only game in town for online contributors spurred to activism by the Trump presidency.

As Shapiro points out, small money’s dominance is not the norm. A New York Times article on the influence of the energy industry’s lobbyists is case in point:

Republican lawmakers were moved along by a campaign carefully crafted by fossil fuel industry players, most notably Charles D. and David H. Koch, the Kansas-based billionaires who run a chain of refineries (which can process 600,000 barrels of crude oil per day) as well as a subsidiary that owns or operates 4,000 miles of pipelines that move crude oil…

…Republican leadership has also been dominated by lawmakers whose constituents were genuinely threatened by policies that would raise the cost of burning fossil fuels, especially coal. Senator Mitch McConnell of Kentucky, always sensitive to the coal fields in his state, rose through the ranks to become majority leader. Senator John Barrasso of Wyoming also climbed into leadership, then the chairmanship of the Committee on Environment and Public Works, as a champion of his coal state.