In the Senate race in Indiana, for instance, Republican Richard Mourdock outspent Democratic opponent Joe Donnelley by about $7 million. But Mourdock lost.

Mourdock ran a strong race, but took a hit in the polls when, at a debate, he made a controversial remark about rape and abortion.

In Wisconsin, Thompson's campaign also hit a few bumps along the way. A low point may have been when Thompson's son told an audience, "We have the opportunity to send President Obama back to Chicago, or Kenya." He later apologized for the remarks.

While the race remained tight throughout election night, Baldwin defeated Thompson 51 percent to 46 percent. Baldwin will become the first female Senator to represent Wisconsin and the nation's first openly gay person to win a Senate seat.

"I didn't run to make history," Baldwin said in her acceptance speech. "I ran to make a difference."

It looks like the money she spent on the race may have made a difference, too.