Peter Russo was an interesting character on the show. At the start of the series, he's a not so notable congressman from Pennsylvania. He's mostly a liar and a semi-bad person. For one he tries to pretend like he's good friends with the new president to gain some power.
But his fortunes turn sour when his bad habits (like strange women and alcoholism) get him into trouble.
He also had some girlfriend I barely remember. She should have dumped him long ago.
He's not much of a congressman either. He often fails to bring anything of worth back home to his people.
But Frank convinces him to run for Governor of Pennsylvania.
Which is a complicated scheme to get him to make a fool of himself, so Vice President Jim Matthews can run and leave his unhappy post in the White House. Which proves to work.
And Frank Underwood commits his first murder by leaving Russo to die in a garage full of carbon monoxide from a running car, after he proved to be far too much trouble for his own good. Frank sure regretted that one in the long-run.