Today’s primaries in six states across the nation are providing a multiplicity of narratives, but the most popular is the one in which the Tea Party is being depicted as the big loser. If polls are correct those Republican candidates most closely identified with the Tea Party are set to lose to politicians who are backed by the so-called GOP establishment. But as with a number of previous elections in which Tea Partiers have lost, this is somewhat misleading. Though some running under the Tea Party banner, like Matt Bevin in Kentucky, are certain losers, that is more a reflection of the weaknesses of these individuals or the strengths of their opponents (in Bevin’s case, Senate Minority Leader Mitch McConnell) than any lack of support for the cause of fiscal conservatism that first swept the nation in 2010.

But once the dust settles after today’s primaries the real question facing Republicans will not be about the future of a Tea Party that has already won due to the conversion of virtually the entire Republican Party to Tea Party principles about taxation and spending. Rather, it will be whether they can define Democratic opponents whose challenges in two key races threaten to prevent the GOP from taking back the Senate. While most of the attention has been focused on the GOP Senate primaries in Kentucky (where McConnell is fending off Bevin) and Georgia where a free-for-all has weakened the party and made a runoff likely, the Democratic standard-bearers are already known. Kentucky’s Alison Lundergan Grimes and Georgia’s Michelle Nunn both look to be formidable general-election candidates.

But more to the point, the GOP intramural fights have allowed both women, who already have the advantage of name recognition stemming from their famous politician fathers, to emerge largely unscathed to this point. While they can expect that to change once their opponents are named, the conceit of both of their campaigns is to run as centrists who are not identified with President Obama or his unpopular ObamaCare legislation. The question is whether or not it is possible for Republicans to convince the public that, in fact, both are liberals who will seek to implement the president’s agenda rather than pursue the centrist course they claim to support. If Republicans can’t define these two challengers in this manner, their chances of winning control of the Senate may be lost.

In Grimes’s case, she has already been under fire from McConnell’s formidable political machine but has, at least to date, been able to portray herself as a centrist alternative to a rabidly partisan minority leader, even if the senator’s primary opponent has absurdly blasted him as a liberal. She can expect those attacks to intensify in the coming months but it is not clear whether efforts to portray her as an Obama acolyte will overcome McConnell’s own low popularity in what polls show to be a dead heat.

But Nunn’s ability to get a free pass from the press and the GOP may have already compromised the Republicans’ ability to hold a seat being vacated by the retiring Saxby Chambliss. To date, Nunn has escaped much scrutiny for refusing to take a stand on most of the president’s policies, even refusing to say whether she would have voted for ObamaCare when it was passed in 2010 or what she would do about the deficit other than the usual empty clichés about stopping fraud and eliminating waste. Unless Republicans can effectively highlight this deceptive strategy, she has a decent chance of winning a Senate seat largely on the strength of being former Senator Sam Nunn’s daughter.

If Republicans want to see what happens to challengers–especially women who are newcomers to politics–when their opponents seek to define them as out of the mainstream, they should look to Oregon where the most formidable GOP Senate candidate seeking the party’s nomination today has been damaged by stories about her supposed stalking of a former boyfriend and husband. Dr. Monica Wehby gained national attention in the last month with her ad titled “Trust,” which featured the parent of one of the patients she treated in her capacity as a pediatric neurosurgeon. Wehby is pretty much a political consultant’s dream in that she is bright, principled, and has no political baggage. As such, she looked to have a better than average chance to put the seat currently held by Democrat Jeff Merkley into play despite the fact that Oregon is a very blue state. But the stories about stalking have put that in doubt. While any candidate is responsible for his or her own behavior, the willingness of Democrats to try to use what appear to be minor, non-violent personal disputes to depict her as a real-life version of the Glenn Close character in Fatal Attraction shows just how miserable a business politics can be.

While Wehby may yet survive this siege, the lesson here for Republicans is that their opponents’ bare knuckles tactics illustrate just how far they are willing to go in order to hold their Senate majority. While hopefully the GOP won’t sink to that level in order to defeat Grimes or Nunn, neither can they sit back and just hope the voters will wake up and realize that electing them is a vote for Obama and Majority Leader Harry Reid, not centrist politics. In an election that hinges on the GOP’s ability to hold its own seats while beating vulnerable Democratic incumbents, the ability to define challengers may be the key to the 2014 midterms.