WASHINGTON — Sen. Kamala Harris is reorienting her presidential campaign strategy to spend far more time in early primary states amid slipping polling numbers for the California Democrat, political aides said Thursday.

Campaign officials insisted the shift was part of a long-planned effort to reach Democrats “when voters are tuning in,” and follows months of focus on fundraising to be able to invest in early states. Harris’ goal, communications director Lily Adams said, is a top-three finish in the Iowa caucuses in February, the first voting in next year’s nomination process.

But the pledge comes as Harris has noticeably ebbed in national polls, recently registering in the single digits and slipping further behind the three leading candidates, former Vice President Joe Biden, Vermont Sen. Bernie Sanders and Massachusetts Sen. Elizabeth Warren.

“You’ve continued to see a sustained investment in Iowa,” Adams said on a conference call with reporters. “This is taking it to the next level.”

Campaign manager Juan Rodriguez added: “This is a conversation about investments that we’ve been planning for some time, and we feel good about where we’re headed.”

The campaign expects to double its paid, full-time organizing staff in Iowa, to more than 130 people. It will also open an additional 10 offices in the state and said Harris will visit Iowa at least once a week in October. She is starting a three-day swing there on Thursday as well.

Visits to other early voting states, including South Carolina and New Hampshire, will also be part of the campaign schedule.

On Wednesday, a reporter overheard Harris telling a colleague: “I’m f—ing moving to Iowa.” Harris campaign staffers spent Thursday morning proudly retweeting the quote.

Harris last visited Iowa in early August, barnstorming the state on a five-day bus tour where she honed her dual message of taking on President Trump and focusing on the issues that keep Americans up at night.

But after that trip, Harris receded from the public eye, spending days off the trail doing private fundraisers. She has been in the Senate for votes just one day since lawmakers came back from their August recess.

Adams said Harris has a “strong operation there in the Senate” to represent Californians, but acknowledged the campaign schedule will affect her work in Washington.

“She’ll to continue to go back as much as she can with the acknowledgment that she’s also a candidate for the president of the United States,” Adams said.

The fundraising time was also key, officials said, as Harris looked to build her campaign war chest ahead of a third-quarter fundraising reporting deadline.

Harris had to spend recent weeks fundraising to keep up with Warren and Sanders, both of them juggernauts at raising individual donations. Aides acknowledged fundraising challenges, but said there were no major concerns.

“You would not be hearing us talking about making investments in Iowa, doubling our staff there, increasing our offices there, if we didn’t feel like we had raised the necessary resources to do that,” Adams said.

After a strong first debate performance, Harris saw a bump in the polls — something Adams called a “sugar high” that the campaign knew would fade. But in recent polls, she has dipped considerably.

An NBC/Wall Street Journal poll this week found her falling to fifth place nationally at 5%, down eight points from its previous survey. An Iowa poll out this week put her in sixth in the state.

Adams and Rodriguez downplayed the slippage, noting that neither of the eventual Democratic nominees in 2004 and 2008 were leading in Iowa at this point in that cycle, and that the majority of voters remain undecided.

“This continues to be a really fluid race,” Rodriguez said.

“When she’s out there more, we do better,” Adams said.

Overtaking her competitors, however, will require those candidates slipping. Adams said Harris would be unafraid to draw distinctions with her competitors during debates, but would be focusing all the same on her own “affirmative message.” Harris is positioned between unnamed Democratic candidates who advocate “going backwards” and others “waging endless ideological battles,” Adams insisted.

Harris is the “best candidate to unify the party and frankly unify the country to get things done,” Adams said.

Tal Kopan is The San Francisco Chronicle’s Washington correspondent. Email: tal.kopan@sfchronicle.com Twitter: @talkopan