The last opportunity in this election cycle for tea party supporters to oust Republican senators arrives with primary elections in Kansas on Tuesday and Tennessee on Thursday.
Democrats, meanwhile, will confront their own party infighting on Saturday in Hawaii.
The Republican divisions have defined the midterm cycle and the contests this week will largely draw those electoral wars to a close for now.
In Kansas, Milton Wolf, a doctor who is running as an outsider, will try Tuesday to topple Sen. Pat Roberts, the 78-year-old who is seeking a fourth term.
Both campaigns have stumbled in a state that has veered to the right in recent years. Wolf, who has attacked President Obama -- a second cousin -- over healthcare, has apologized for posting insensitive commentary about patient X-rays loaded onto his Facebook page. Roberts has tried to show he's in touch with the state after it became known that he no longer keeps address there other than a rented room in a friend's home.
Neither the race in Kansas -- nor Thursday's contest in Tennessee -- have seen the influx of outside spending that poured into other tea party battlegrounds, and both states are likely to return Republicans to the Senate in fall.
In Tennessee, two-term Sen. Lamar Alexander, a former governor and Education secretary, is fending off a challenge from conservative Joe Carr, a state legislator whose campaign has been using Twitter to drum up support.
Despite the high hopes of tea party groups, most of their efforts to oust Republican senators this year have fizzled -- with the exception of the continued standoff in Mississippi, where tea party favorite Chris McDaniel is challenging his loss during the runoff against Sen. Thad Cochran.
In fact, the most notable upset of the primary calendar drew scant attention from national tea party groups -- the toppling of House Majority Leader Eric Cantor by a little-known economics professor in the suburbs of Richmond, Va.
The splintering of the GOP at a time when Republicans are trying to net six seats to take control of the Senate has caused hand-wringing among some party leaders.
But Reince Priebus, the chairman of the Republican National Committee, shrugged off the internal debates as helpful exercises to produce the best candidate.
"I'm not one of these people that buy into the theory that primaries are bad," Priebus said in a recent interview on Capitol Hill. "I think primaries can actually make candidates stronger."
Democrats have largely avoided a similar level of party infighting, except in Hawaii, where Sen. Brian Schatz, the Democrat who was appointed by Gov. Neil Abercrombie after the death of longtime Sen. Daniel Inouye, on Saturday faces Rep. Colleen Hanabusa, who was considered the ailing senator's favored replacement.
Abercrombie's decision to pick Schatz, who at the time was lieutenant governor, also contributed to the governor's own primary challenge Saturday.