In this space, I’ve talked about several instances in which Republicans have attempted to bring down a local Democrat by linking him or her to Barack Obama. And, as the slide show given by House Republican leader John Boehner showed, Republicans clearly plan to take the strategy national.

Bad news for the Republicans, then: In Louisiana, where they tried to bring down Don Cazayoux by using the looming specter of Obama against him, they failed.

In one ad run against Cazayoux, Republicans said, “A vote for Don Cazayoux is a vote for Barack Obama and [House Speaker] Nancy Pelosi.” Another also brought up Obama and Pelosi, who had also been discussed in Boehner’s strategy presentation. “Is Obama right for Louisiana? Is Pelosi? You decide,” that ad said.

But on Saturday, Cazayoux won his race, taking over a seat held by Republicans for years. As the Wall Street Journal notes in its story on Cazyoux’s election, “The victory could aid Sen. Obama in making his case to uncommitted, elected superdelegates wary of how the top of the ticket could affect their own races in November.”

Update: In comments, a couple of readers have pointed to what the National Republican Congressional Committee told the WSJ:

The NRCC said that linking Mr. Cazayoux with Sen. Obama and Rep. Pelosi was effective because Mr. Cazayoux had a wide lead in polls heading into the race. A SurveyUSA poll commissioned by Roll Call newspaper favored Mr. Cazayoux to win by nine points; he won 49% to 46%.

“What we do know is that a Democrat was clearly favored to easily win this election before Republicans invoked the names of Barack Obama and Nancy Pelosi,” the NRCC said in a memo. “This should come as a warning shot to Democrats.”

That explanation doesn’t really hold water. First, SurveyUSA’s polling was done after the attacks on Cazayoux began. As Roll Call reported:

Despite enduring two weeks of constant attacks on the air from Republicans and independent conservative groups, Cazayoux had a net favorability rating of plus-15 (43 percent favorable, 28 percent unfavorable and 28 percent neutral or unfamiliar), according to the poll… Despite an initial hesitancy over whether to even play in the race because of the baggage Jenkins brought to his campaign… the NRCC has committed significant resources to the contest. According to Federal Election Commission filings, the committee has dropped more than $325,000 in independent expenditures on the race in just the past two weeks… “By the looks of Don Cazayoux’s ads, he is on the defensive,” NRCC spokesman Ken Spain said Wednesday. “His support for Barack Obama’s radical health care agenda and his long record of raising taxes is becoming a growing liability for him.”

Also, according to Roll Call, SurveyUSA included this disclaimer in a memo about its results: “if voters are older and/or whiter than SurveyUSA here foresees, the Republican will outperform these numbers.”

And finally, the SurveyUSA poll had a margin of error of plus or minus 4.5 percentage points. Cazayoux won by 3 points — that result is within the margin of error.