Hey Courtney,
If you're looking to capture UTM parameters via auto-tagged links and put them into hidden fields, you're mostly going to be out of luck. Auto-tagging uses "gclid" unique values, which are mostly indecipherable to anything except for Google Analytics. Manually tagging AdWords ads will give you the required level of specificity if you need medium/source/keyword level granularity.
I find the best compromise is to have separate programs for your channel and vendor with unique landing page URLs, which will give you bubble-up reporting on how big initiatives are turning into volume of leads and costs per lead. Then so long as conversions are being recorded, you can optimize within the native tools (GA and AdWords interface).
Having a separate program and separate landing page URLs also helps because you can optimize more quickly and accurately. It becomes pretty quick to clone a landing page and then tweak the content so you can get a higher quality score (and therefore lower CPC) per group and specific ad tailored to the keywords and ad copy. And because the URLs are unique to your advertising (aka, aren't accessible except through those ads), you can more confidently say "leads who converted on that landing page are attributed to the success of those paid advertising efforts" without worrying if someone came back with crazy navigation and was falsely attributed as a success.
If you didn't care as much about the quality score of landing pages and just wanted straight-to-the-point and easy, you could watch for people converting when their URL contained "gclid" at any point—you'd only be able to see if someone came from AdWords or not, and not see any other specificity from that, but depending on your business case that might be an appropriate path.
Best,
Edward Unthank | Founder, Etumos
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