I'm hoping to track the initial lead source for all of our leads, not just ones that come to our website via a tagged URL. I've read other threads in the community regarding capturing lead source by using UTM fields, but my concerns with this are:
1) We will only capture this source information for users that visit our website via outbound links (things we share on social, email, etc.) and fill out a form.
2) This would cause our data to be inaccurate, as this isn't necessarily truly the "initial lead source". For example, a visitor may be referred to us from a website, but then follow us on Twitter, later clicking a link we've shared and filling out a form. This method would lead us to believe the initial lead source was Twitter, when it is instead a referral.
Is it possible to pull this same information that Google Analytics stores (source, medium, etc.) for all visitors to our website? If not, how can I collect more accurate information regarding initial lead source?