New Hampshire
Though New Hampshire leans blue, Sen. Jeanne Shaheen (D-N.H.) is vulnerable if Republicans can field a strong challenger. Outgoing Gov. Chris Sununu (R) would be a dream candidate for conservatives, given his widespread popularity and record of results. While he has expressed disinterest, the GOP can still rally around a proven leader to give Shaheen her toughest challenge yet.
Susan Collins needs to be primaried. There has to be better Republican in Maine than Collins.