D'Amboise is known by just 5 percent of Maine Republicans, while Dodge's name id stands at just 2 percent. In an early ballot test, Snowe led both candidates easily with 43 percent of the vote to 18 percent for D'Amboise and 10 percent for Dodge.

Snowe's approval rating among Republican voters in the state is also a net positive. A full 47 percent of Republicans approve of her performance, compared to 44 percent who disapprove. 

Late last year, Gov. Paul LePage (R), who won election with strong support among Tea Party activists, said he will support Snowe's reelection for purely personal reasons. LePage has a history with Snowe's late husband and said his relationship with the Snowe family "transcends politics." 

It's still possible other challengers will jump in the primary against Snowe, and pollster Tom Jensen notes that both Sen. Lisa MurkowskiLisa Ann MurkowskiRepublicans jockey for position on immigration GOP senator knocks Trump: 'Not a fan of governing by tweet' How the effort to replace ObamaCare failed MORE (R-Alaska) and Rep. Mike Castle (R-Del.) had solid approval ratings among Republican voters at this point last cycle. 

The Tea Party Express has also announced its intention to play a role in the race. And, as evidenced last cycle, that can translate to a sizable amount of ad money and considerable national attention.