Joe Walsh’s anonymity is dissipating and, by the time it’s gone, we may have an answer to an intriguing political question.

If you win in anger, can you govern in anger?

Mr. Walsh was not just a little-noticed congressional candidate in Chicago’s northwest suburban 8th District. He was radioactive to most establishment Republicans, who were miffed over his surprise primary victory and gave him scant help and money during the general campaign.

Deemed extreme by Republican honchos, Mr. Walsh  an unabashed Tea Party member, a business consultant and graduate of the University of Chicago’s public policy school  stunned Melissa Bean, the incumbent moderate Democrat, even though he had been dramatically outspent.

John Shimkus, a Downstate Republican congressman, jokes that the Republicans won five of their four targeted congressional districts in Illinois. Few imagined a Walsh victory.