Some Republicans are growing worried that two key Senate races once considered critical to holding their majority are slipping from their grasp.

In more than a dozen interviews with campaign officials, senators and operatives, there is recognition that North Carolina and Georgia are looking less competitive than the party once anticipated and that decisions need to be made soon about whether to keep investing, even as party officials insist they are not walking away from their candidates there.

Republican senators like North Carolina Sen. Thom Tillis, said it was time for the party to make some tough decisions about spending.