The National Republican Senatorial Committee said Thursday it is making a last-minute investment in the Wisconsin Senate race, which is tightening up unexpectedly in the final days of the campaign.

The committee will spend close to $1 million in several media markets, including Milwaukee and Green Bay, on behalf of the GOP incumbent, Ron Johnson. Long considered one of the most vulnerable senators, Johnson faces a challenge from ex-Sen. Russ Feingold, the Democrat he beat six years ago, in a state that favor Democrats in presidential election years.

Private and public polls show a single-digit difference between the candidates.

The new spending in Wisconsin comes as Republicans are battling ferociously to protect their 54-46 majority in the Senate ahead of Tuesday’s election. They are on defense around the country, but a number of close races are essentially toss-ups in states such as Pennsylvania and New Hampshire.

Republicans say they have regained momentum after the FBI’s announcement last Friday that it is looking into a new batch of emails in connection with Hillary Clinton’s handling of classified material.

The committee’s ad accuses Feingold of changing during his three terms in the Senate, alleging he enriched himself. “Russ Feingold’s hypocrisy is Washington at its worst,” the ad says.

(AP)