CONCORD, N.H. — A slew of advertising in contested primaries for governor is hitting the television airwaves in the week before voters head to the polls.

Polling shows most of the seven major candidates for governor — three Democrats and four Republicans — are unknown to many New Hampshire voters. In the final stretch, television ads provide a quick, though costly, way for candidates to boost name recognition.

The primary election is on Sept. 13. The candidates are seeking to replace Democratic Gov. Maggie Hassan, who is running for a U.S. Senate seat.

Many of the ads are biography-focused. Democrat Mark Connolly, for example, talks up his job as the state’s financial watch dog in the mid-2000s, while Democrat Colin Van Ostern discusses his previous job working at Stonyfield Yogurt. Republican Frank Edelblut talks about exposing fraud at a company he worked for and starting up his own business.

But some of the ads are turning negative in the final stretch.

Republican Manchester Mayor Ted Gatsas is up with an ad attacking fellow Republican Chris Sununu as too liberal. Sununu, in response, has launched an ad calling Gatsas desperate.

Both also are running other ads, with Gatsas’ focusing on his time as mayor and Sununu’s on his role as chief executive of Waterville Valley ski resort.

Two candidates, Democrat Steve Marchand and Republican Jeanie Forrester, have not booked any ad time on WMUR, according to available documents, while Van Ostern and Gatsas have purchased the most airtime.