Fundraising emails from both campaigns have been fast and furious this year, and many from Team Obama got personal with subject lines such as "Hey" and "Dinner?"

Jon Stewart, the host of Comedy Central's "The Daily Show" and a favorite of the president, mocked the plethora of emails in a segment last April. 

"Seriously, there are exiled Nigerian princes getting Obama campaign emails going, 'Ease up on the money thing, fella,' " Stewart joked.

Since April, the emails have gotten even denser. The day before the final Federal Election Commission (FEC) fundraising deadline last Wednesday, Team Obama sent out four. And Romney attended his final fundraiser of the cycle Saturday, but on Tuesday he is still signing emails fundraising on behalf of "the Republican team."

It turns out less than half those emails are read on a regular basis. 

Return Path, a leading email intelligence firm, analyzed the effectiveness of all those emails based on a random sample of how two million inboxes treated email from the presidential campaigns over the course of about a month earlier this fall, and provided the infographic below.