The run-off election to fill Duke Cunningham's vacant Congressional seat in San Diego is this Tuesday. Polls have shown Democrat Francine Busby with a small lead in this heavily Republican district. It's going to be close, but this could be a huge victory for the Democrats.
If Busby wins it will start an avalanche 0f stories about how the Democrats can now win in areas where they never had a chance before. The press will change the conventional wisdom of how big the Democratic victory will be this November. It will put the words "Democrat" and "victory" side by side in lots of people's heads and everyone will know that the mid-term election will be historic. It doesn't even matter that Busby will have to defend her seat again in November, if she can win on Tuesday she can have a huge impact on all the elections to come.