Sen. Rob Portman, R-Ohio, center, speaks with reporters as he arrives for a vote on an energy bill he co-sponsored with Sen. Jeanne Shaheen, D-N.H., at the Capitol in Washington, Monday, May 12, 2014. (AP Photo)

Sen. Rob Portman (R-Ohio), a vice chairman of the National Republican Senatorial Committee, said Thursday that he does not think any Republican-held Senate seats are in "great danger" of falling into Democratic hands and that the battle for the majority will probably come down to a handful of races that are "too close to call."

Speaking at a Christian Science Monitor breakfast, Portman sounded optimistic that Republicans running in Georgia, Kentucky and Kansas would hold GOP-controlled seats.

Senate Minority Leader Mitch McConnell (R-Ky.) is "going to be fine" against Secretary of State Alison Lundergan Grimes (D), Portman predicted. He said Republicans are "doing well" in Georgia, where businessman David Perdue (R) faces Democratic philanthropist Michelle Nunn.

In Kansas, Portman said Sen. Pat Roberts (R) is "doing fine." But the NRSC recently dispatched a top strategist to rescue Roberts's campaign amid concerns about his lackluster effort as independent challenger Greg Orman has surged. Orman won't say which party he'd align himself with in the Senate.

Republicans need to gain six seats to win the majority. Portman expressed confidence Republicans would pick up Democratic-held seats in West Virginia, South Dakota and Montana.

Beyond that, he said there are a handful of states that are "too close to call" and will probably determine the majority. Among them: North Carolina, Arknasas, Louisiana, Iowa, Michigan, Colorado, New Hampshire and Alaska, all states controlled by Democrats.

Asked whether the NRSC would devote substantial resources to states they are defending, Portman responded, "I'm hopeful we won't have to." The NRSC has already spent money on advertising in Georgia.

Portman recently said in an interview with The Washington Post that he might consider running for president in 2016. He recently traveled to New Hampshire, an early nominating state, stoking speculation he's gearing up for a bid.

He said Thursday that after the midterm election, he plans to "take a look" at running.

"My daughter goes to school up there, so part of my heart is in New Hampshire," said Portman.