(NewsNation) — While former President Donald Trump appeared in a New York courtroom Thursday, his Republican rivals hit the campaign trail in Iowa fresh off their latest debate.

Former South Carolina Gov. Nikki Haley touted her strength in recent polling in a hypothetical matchup against President Joe Biden.

“Ron doesn’t defeat Biden. Trump is head-to-head with Biden. On a good day, he might be up by two. In every one of those polls, I defeat Biden by double digits — 17 points in the Wall Street Journal poll,” Haley told voters.

While Trump has been lashing out at prosecutors in his civil case in New York, his senior adviser maintains that his ground game remains strong even without Trump’s physical presence in Iowa ahead of caucuses.

“Fact of the matter is President Trump has put together a very serious, very strong ground game here in Iowa. It doesn’t matter if it’s snow, we have a blizzard forecast, everything going on — our people are out putting up signs and knocking on doors,” Trump campaign senior adviser Jason Miller said during an interview on “The Hill on NewsNation.”

Even with Haley surging in recent polls, Miller is confident Trump will take the victory.

“President Trump is going to win on caucus night. He’s going to win in New Hampshire. He’s going to win the nomination,” Miller insisted.

A new poll of likely Iowa caucusgoers by Suffolk University shows Trump is still dominating the field in the Hawkeye State with 54% support. Haley trails behind the former president with 20%, and Florida Gov. Ron DeSantis follows with 13%.

Iowa and New Hampshire are among the early states often looked at as signals for the rest of the election cycle.

The Hill contributed to this report.