Democratic presidential hopeful Bernie Sanders plans to start a robust television advertising campaign next month in Iowa and New Hampshire, two states where Hillary Rodham Clinton has been on the air since August, a senior strategist for Sanders’s campaign said Wednesday.

Word of the decision comes as some recent polls have shown Clinton increasing her lead nationally and erasing Sanders’s lead in New Hampshire, the nation’s first primary state. Many analysts have attributed Clinton’s uptick to a strong debate performance last week.

Tad Devine, a veteran Democratic consultant advising Sanders, said another factor is the head start Clinton got in communicating with voters on television in Iowa and New Hampshire.

“We’ve gone through two and a half months of unanswered paid media,” Devine said. “They’ve put up enough paid media to get someone elected governor or senator in those states.”

Devine would not discuss the particulars of Sanders’s planned ad campaign but said it is likely to start next month in Iowa and New Hampshire and that Sanders would be on the air not too long afterward in Nevada and South Carolina, two other states with early nominating contests.

“We’re not saying the day,” Devine said. “We’d like there to be an element of surprise.”

Sanders, an independent senator from Vermont, has pledged to continue his tradition of not running negative ads. A five-minute video on his Web site provides a feel for what his advertising is likely to look like (in shorter form).

Sanders finished the most recent fundraising quarter with nearly as much cash on hand as Clinton. He reported having more than $27 million in the bank, while Clinton said she had about $33 million at the end of September.

Strong fundraising since then has Sanders well-positioned to launch his television advertising, Devine said.

Devine also said Wednesday that Vice President Biden’s decision not to enter the Democratic presidential race would not have much direct effect on Sanders's messaging or campaign activities.

"I think the real impact, if there is one, is the race is a little clearer, a little cleaner for voters," Devine said. "It's now binary. It's Hillary vs. Bernie. I think voters can now look at the two candidates who are in front, and that makes it really important for people to understand the choice."