MANCHESTER, N.H. — Senator Bernie Sanders, who came within half a percentage point of defeating Hillary Clinton in Iowa, will spend the next week trying to maintain a significant advantage in New Hampshire, where he has been leading in polls for months.

His campaign will stage rallies in the more populous southern parts of the state, where he also will air more than $1 million worth of television ads.

“Now we have a two-way race, one-on-one, and it is going to be played out here in New Hampshire,” said Tad Devine, a senior strategist for the campaign.

To hear the Sanders campaign tell it, the close race in Iowa established the Vermont senator as a viable alternative to Mrs. Clinton and raised his profile with voters around the country. Now, campaign officials say, they hope a New Hampshire victory will help him press forward by generating excitement among voters in later-voting states and bringing in money for his upstart campaign, which raised more than $1 million in the 90 minutes after his speech Monday night, according to Michael Briggs, campaign spokesman.