This Wikipedia article could be interpreted to indicate that members of the Republican party, based solely on number of instances, are ~2.5x as likely to be corrupt than members of the Democrat party.
Members of the Democratic party (D) involved in corruption: 74
Members of the Republican party (R) involved in corruption: 186
Total instances of corruption in the US: 260
Edit: A fair observation is that, although the name remains the same, the party changes, so, as per comment suggestions, I did the same calculation, but from 1964 and to today, which doesn't make matters much better, Republicans are still 2.3x as likely to appear in the list as democrats are. Here are the numbers for the revised period:
Members of the Democratic party (D) involved in corruption: 57
Members of the Republican party (R) involved in corruption: 130
Total instances of corruption in the US: 187
There are, of course, a few reasons that this approach is simplistic, but, in my opinion, none of them explains the magnitude of the distribution imbalance.
Simple-1: The Republican party has a head-start on the Democrats, their first entry is from 1842, and the Democrats first entry is from 1856, if you use 1856 as the starting year, to level the playing field, deduct 1 (Charles F. Mitchell) from both the Republican and total tallies.
Simple-2: The makeup of possible entrants on this list could vary, in my opinion, the partisan makeup of congress should be a reasonable expression of this (I realise that officials can be taken from outside this pool, but, I still believe it is reasonably representative of the possible entrants on the list). I compiled this list taken from this Wikipedia page to break down the numbers, which shows that, since the 35th congress, fewer congressmen have been Republicans, compared to Democrats (20459 to 18596, or 52.4% Democrats to 47.6% Republicans).
Simple-3: These are only discovered and reported instances of corruption, and even as wealth can help (not guarantee) you to avoid either of those, again, I couldn't think of a reason why that would favour one party over the other.
Simple-4: Source diversity. All my numbers are taken from Wikipedia, which is not unbiased, but according to this article (yes I see the irony, but there are links to follow to the original study, I believe linking to the Wikipedia article will help summarise the conclusion to lazy readers) the bias runs both ways, on different subjects, so my assumption is that when it comes to pointing out corruption in the opposition, the two sides will, more or less, cancel each other out.
Edit: Simple-5: The data completely ignores the magnitude of the offence, so an answer could be that republicans commit a higher number of less grievous counts of corruption while Democrats commit fewer more grievous counts. It could also be the other way around and the bar for when it is either considered corruption, or just discovered, could be in the Democrats favour. I'm unaware of any standard definition of "corruption", but I assume there must be one, as there have been conducted formal, international studies on the subject.
Considering the above premise, can anyone come up with an explanation for the distribution of the numbers?
A simple script (Linux, as I am a Windows-illiterate) parsing the mentioned web page, in laymen terms, this is what it does:
- Assumes that all instances of corruption is prefixed with a '*' and includes the perpetrator and political affiliation in the first line (120 characters, arbitrary definition of line, but it resulted in no duplicates and I can't think of a reason it'd favour one party over the other)
That the political affiliation of the perpetrator is identified in one of two ways:
2-1. As a simple one-letter (either 'D' or 'R') in parentheses right after the name of the perpetrator.
2-2. As a one-letter abbreviation, followed by a hyphen ('-').
Any instances not matching either of these parameters are simply discarded, this means Whigs and independents (there appears to be no instances of Independent-perpetrated corruption listed) are not considered, neither in the total of either party nor in the grand total.