Ed Garvey proved in his 1998 campaign for governor of Wisconsin, disclosure alone is mostly confusing. The Garvey campaign reported every contribution as it came in and posted it on their campaign web site. This revealed almost nothing. To disclose anything contributions have to be organized by source, and even that is revelatory only after going behind some of the contributions to get past the beards and the launderers. Even this isn't explicitly revealing until and unless disclosure can be tied to activity.
X gives money.
Y takes the money. Y moves X's bill out of committee. Public funding and taking on television the 1,000 pound gorilla are harder. But the tactics used to ban or subvert the independent campaigns should work on excessive spending on other things and from other sources as well. And the parallel postcard campaign the school choice zealots mounted to make sure Jon Wilcox remained on the state supreme court has come back to haunt them and him.