[nkurz]

This is a wonderful comment, but I fear you still might be underestimating the problem. Even if you replaced the two-party system with any other number of parties, you'd still never have a party dedicated to each issue. Voters will always be choosing a candidate who supports the majority of their views, and small issues such as this one will almost never be the deciding factor between the available candidates.

Making it worse, these issue-specific lobbyists don't really care which individual (or party) wins the election, just that the votes on the few bills that their funders care about go in their desired direction. So they can simply make it known after the election that anyone who votes in their preferred direction can expect to receive a "donation" funding their reelection campaign.

But helping the candidate get reelected isn't the only way that lobbyists can help a candidate. Instead, they could donate to the candidate's nonprofit family foundation, give the candidate's family members well paying board seats, wait until their retirement and overpay the candidate for lectures. Once word gets out that candidates who vote in a particular direction are given future preference of any sort, the lobbyists are pretty assured of getting what they want regardless of what the campaign finance laws say.

Short of finding some hidden trove of non-corruptible and non-self-interested politicians, I don't think there are any easy fixes for this. Unless you can find a way that "representatives" are unable to derive personal benefit from their votes and are compelled to put their constituents interests above their own, the system will be vulnerable to being swayed those able to offer that benefit.