Mississippi's Sen. Thad Cochran pulled off a difficult and surprising win Tuesday night, and he has the state's open primary law to thank for it. In the June 3 primary, Mr. Cochran trailed tea party favorite Chris McDaniel by 1,386 votes or 0.5% of the 313,443 votes cast. This week, he beat Mr. McDaniel, a state senator, by 6,373 votes or 1.6% of 374,893 votes.
Turnout was up in the runoff, which last happened in a Senate race 30 years ago. The six-term senator's victory was due to a strategy by his campaign and the support of the Mississippi Conservatives super PAC led by GOP national committeeman Henry Barbour and his uncle, the very popular former Gov. Haley Barbour. They aimed to turn out for the second-round Republicans who did not vote in the primary and bring out Mississippians, including Democrats, who had not voted in either party's primary and thus could vote in the runoff.
These organizational efforts paid off, with turnout increasing in counties Mr. Cochran carried in the first round at about twice the rate as turnout rose in counties Mr. McDaniel won. (Full disclosure: I donated to Mr. Cochran's campaign and the super PAC that I help, American Crossroads, donated to Mississippi Conservatives in the primary and runoff.)
Some new runoff voters were blacks drawn to the polls by an anti-tea-party message, others were Republicans who had taken the first round for granted, believing that Mr. Cochran would win handily. Mr. McDaniel cannot complain about crossover voting since he participated in the 2003 Democratic primary.
This political near-death experience for Mr. Cochran should not obscure truths that Republican officeholders ignore at their peril. Members of Congress had better stay connected to the politics of their state or district if they hope to win re-election. That doesn't mean incumbents need to be in lock-step with every group on every issue. It does mean holding town hall meetings, staying in touch with local political leaders, listening to their concerns, treating them with respect by telling them when and why one disagrees, and cultivating allies.
Mr. Cochran's comment earlier this year that the tea party "is something I don't really know a lot about" helps explain why Mr. McDaniel had an such a golden opportunity to knock off the incumbent. Mr. Cochran was first elected to the House in 1972 and Senate in 1978.
There was also a primary Tuesday in Oklahoma to fill the seat about to be open due to Sen. Tom Coburn's pending retirement. As in Mississippi, the so-called establishment choice, Rep. Jim Lankford, defeated the tea party favorite, former state House Speaker T.W. Shannon, a rising star who was helped by many of the same national tea party groups that aided Mr. McDaniel. But many Oklahoma tea party groups aided Mr. Lankford or remained neutral while criticizing outside interference. Mr. Lankford was first elected in 2010 and was considered a tea party supporter by many groups in the state.
Tuesday's outcomes suggest local tea party groups have more influence than the national groups purporting to speak for them. A network of Mississippi tea party groups made Mr. McDaniel competitive. In Oklahoma, national groups like Club for Growth, Senate Conservative Fund and FreedomWorks could spend and endorse all they wanted, yet local tea party support for Mr. Lankford blunted these inside-the-Beltway groups' impact in the Sooner State.
This has happened a lot this year. Republican incumbents in Kentucky, South Carolina and Texas, and GOP Senate candidates in Arkansas, Colorado, Georgia, Montana, North Carolina, South Dakota and West Virginia all avoided or vanquished tea party challengers by keeping close to their state's politics and offering a message that grabbed a significant slice of local tea party support.
Eight of nine GOP House members targeted by the Club for Growth escaped serious opposition and the one who did face serious opposition won 2 to 1. On the flip side, every national tea party group sat out the June 10 Virginia Seventh Congressional District primary. Local tea party groups provided the volunteers and enthusiasm that propelled David Brat to his stunning victory over House Majority Leader Eric Cantor.
Former House Speaker Tip O'Neill once famously said, "All politics is local." That doesn't mean politics is only local or that lawmakers should only reflect the views of some groups back home at every moment. But constituents do want to know they're being heard rather than forgotten. Politicians who forget that ancient lesson pay a price sooner or later.
A version of this article appeared June 26, 2014, in the U.S. edition of The Wall Street Journal, with the headline National Tea Party Groups Take A Beating and online at WSJ.com.