This was an open seat. Candidates running were Democratic nominee Ann McLane Kuster, Republican nominee Charles Bass, Libertarian nominee Howard Wilson, and Independent candidate Tim vanBlommesteyn.
In February 2009, Republican U.S. Senator Judd Gregg was briefly nominated to be President Barack Obama's Secretary of Commerce, but withdrew. Gregg announced after withdrawing his nomination that he would not run for re-election, leaving the seat open. Democratic incumbent Paul Hodes had announced his candidacy for the seat while Gregg had been nominated but had not yet withdrawn.
On the Republican side, former state Representative Bob Giuda declared his candidacy for the seat. The 2008 Republican nominee for this seat, Jennifer Horn, announced her intentions to run a second time on October 7, 2009. Former six-term Congressman Charles Bass formed an exploratory committee to run for this seat on October 1, 2009 and later formally filed. In the resultant Republican primary, Charlie Bass narrowly defeated Jennifer Horn, with Giuda far behind.