If you have the ability to track the number of visitors to your website (I think the FSF recommends piwik for this) then you can get a rough measure of whether

If you have the ability to track the number of visitors to your website (I think the FSF recommends piwik for this) then you can get a rough measure of whether that number goes up noticeably in the time after a campaign, especially if you filter by IP addresses in the geographic area. No need for unique URLs.