The mild furor over Sen. John McCain’s constituent work might be so much political sturm und drang, were it not for the irony: The Senate’s leading champion of campaign finance reform, and the Republican presidential hopeful who has made washing dirty money out of the political system a top priority, is accused — in roundabout fashion — of providing political payola to campaign contributors.

It is in those accusations, however, that one sees the merits behind McCain’s deep desire to rid our political system of plutocracy.

Recent media reports show Sen. McCain writing to various federal agencies on behalf of people who have given his campaigns money — often, within a few weeks of having received a donation. Because Sen. McCain oversees many of the agencies in question as chairman of the Senate Commerce Committee, the implication is that the Arizona senator abused his position in response to campaign money he has received.

In his defense, Sen. McCain rightly notes that it is his job to hold federal agencies responsible for their performance under the law and to assist his constituents. And it’s apparent from the context and content of the letters McCain has sent that all he requested was action within the scope of the law — not a specific outcome.

While whether the senator from Arizona would make a good president remains something for the Republican Party and the American people to determine at a later time, the one thing he should not be accused of is duplicity on campaign finance reform. He has remained a steady voice in the call for purging big money from politics, and his leadership has been instrumental in achieving what few victories have been had on this front — often, with his own party’s leadership the largest impediment to the progress he sought.

The entire scrap over the letters Sen. McCain wrote bears out the central point and problem behind unfettered campaign contributions: Even people like the senator, whose record on this issue is ironclad, can and will come under suspicion when big contributors hand over a check.

Until we get rid of the big spending in politics, we will never have a political system worthy of implicit trust. The political pillory in which Sen. McCain has been locked may be an unjust punishment for him, but it clearly demonstrates how the entire political process is shackled, so long as big corporations and political interests continue to purchase influence.