Former Massachusetts Sen. Scott Brown (R) will announce he's running against Sen. Jeanne Shaheen Jeanne ShaheenRussian interference looms over European elections Restore funding to United Nations Population Fund Senators urge Tillerson to meet with Russian opposition activists MORE (D-N.H.) in New Hampshire on Thursday, The Hill has confirmed.
He has long been expected to run. Brown has flirted with a bid for months, moving from Massachusetts last year. He has been on a month-long "listening tour" in which he's publicly discussed a challenge to Shaheen, and said last week that he would definitely run against her.
Shaheen has led in most public polls by a high-single-digit margin.
WMUR first reported the news of Brown's decision.
—This post was updated at 9:08 a.m.
Alexandra Jaffe contributed to this report.