Google latches onto key words and sends advertising that corresponds. Does that to your gmail, too. I remember once I was discussing the old TV series Starsky and Hutch on my email and advertisements for rabbit hutches kept coming up. LOL
If you're talking about Republicans, ads come up encouraging you to "fight Liberal power mongering" but if you're discussing Democrats, ads come up encouraging you to go to websites that blast Tea Baggers and George W. Bush.
Google has no opinions, it's just there to make $$$$$ by sucking up to you. LOL