With the National Republican Congressional Committee throwing a little money Jennifer Horn's way, it's worth considering what it would take for the Republican nominee to unseat Democratic incumbent Paul Hodes in his first bid for re-election. 

The place to start thinking about this is the top of the ticket.  Unless things change drastically in the next three weeks (and hey, who knows?), Horn will have to win some percentage of Obama's vote in the 2nd Congressional District in order to upset Hodes. 

Scenario No. 1: Let's consider a scenario very favorable for the Republicans: John McCain defies current polls and carries New Hampshire in a nailbiter, 50 percent to 49 percent. 

A one-point McCain victory statewide likely works out as follows in NH-2: Obama wins 51 percent of the vote, McCain 48 percent. This assumes that Obama, like John Kerry four years ago, runs a couple points better here than statewide.  (In 2004, Kerry won the state 50-49 and NH-2, 52-47.)

If Obama wins 51 percent of the vote in her district, this means that Horn has to find a way to break off part of the Obama vote for herself. To win her race 50-49, she would have to earn 104 percent of McCain's vote. Conversely, Paul Hodes would have to underperform Obama by 4 percent.  A "net" 4 percent of Obama voters would have to swing to Horn as they filled out their ballots. (This analysis assumes that voters fill out their ballots completely, or at least that Obama voters are as equally likely as McCain voters not to do so.)  

Four years ago, 4 percent of John Kerry's vote equaled 7,100 votes.

Scenario No. 2: Now suppose Obama's lead melts in the last few weeks of the campaign, but he barely hangs onto a 50-49 victory statewide.  In that case, Obama carries NH-2, 52 percent to 47 percent.

Horn's task becomes a bit harder. She now has to earn 106 percent of the McCain vote in order to win a one-point victory.  Hodes would have to underperform Obama by 6 percentage points. The Obama "swing vote" to Horn climbs to 6 percent. 

Scenario No. 3: Obama carries the Granite State by five points, 52-47.  This translates into a nine-point Obama victory in NH-2, 54-45. 

In this adverse environment for a Republican, Horn would have to earn 111 percent of McCain's vote. Hodes would have to underperform Obama by 9 percentage points.   Roughly one of ten Obama voters have to swing over to Horn. In 2004 terms, that's about 18,000 voters. 

That's the dilemma for Horn: In the face of a quite plausible Obama victory in her district, she has to find a way to convince a significant number of Obama voters to fire the incumbent Democratic congressman and install her in his place.  For Horn to win, there may well have to be thousands more Obama-Horn voters than McCain-Hodes voters.