The ability to corrupt is inversely proportional to how active our citizens are in the political process.

Only like 10% of eligible voters vote in primary elections. That likely makes it far easier for money to buy enough name recognition via advertising to make a financially backed candidate a shoe in. But if you look at something like the NYC mayoral primary, a grassroots movement with support still beats moneyed interests.

That said, our country does a lot to discourage participation in our political process.