Much is being made this season of the fact that Democrats are winning special elections in districts normally held by Republicans. This happened once in March and twice earlier this month in special elections for Congress. All three elections were in districts that Republicans had controlled for decades, and yet Democratic candidates managed to win all three, prompting members of both parties to predict a Democratic landslide in November. Timothy Russert declared that a seismic shift is afoot, and Congressman Tom Davis of Virginia wrote that House Republicans face the worst political atmosphere since Watergate.

But feature this fact. Of the three Democratic candidates to win seats, only Bill Foster, who won the seat in Illinois vacated by the former speaker, Dennis Hastert, seems in tune with his party’s national leaders. Mr. Foster’s success owes more to circumstances particular to that campaign than to any seismic shift in American politics. It no doubt helped, for instance, that Mr. Foster’s Republican opponent, James Oberweis, had failed to win his last three campaigns. The rise of the junior senator from Illinois to national preeminence has to be a boon to Democrats throughout his home state.

The other two Democratic congressional victories took place in the Deep South. Donald Cazayoux won Louisiana’s sixth district, and Travis Childers won Mississippi’s first. What auguries are Democrats — or, for that matter, Republicans — to take from these victories? In his campaign advertising, Mr. Childers managed to say that he is a fiscal conservative, pro-gun, and pro-life. Mr. Cazayoux’s politics are identical on these three issues, and like Mr. Childers, he emphasized these conservative positions throughout his campaign. Is this the winning formula for the Democrats in 2008?

Then there’s one of the most unlikely political scandals of the season. It involves Democrat Mr. Childers getting caught falsely denying that he received support from his party’s likely standard bearer, Mr. Obama. “Taking Obama’s support is wrong,” said a sinister voice in a negative ad against Mr. Childers. “Lying about it is even worse.” Asked the interviewer in a local news segment: “Would you accept Mr. Obama’s endorsement?” Mr. Childers visibly grimaced, as though he’d been given a particularly difficult math problem, and then answered a question no one had asked.

Republican opponents of both Messrs. Childers and Cazayoux tried to discredit their claims to conservative values by associating them with the liberalism of prominent Democrats like Mr. Obama and Nancy Pelosi. Some Democrats have pointed to the failure of these tactics as an indication that liberalism is gaining support in these districts. Stephanie Grace, of the New Orleans Times-Picayune, has a more persuasive theory. “Congressional campaigns here have often faltered when they focused too much on partisanship,” Ms. Grace writes, citing Senator Landrieu’s victory over Suzanne Haik Terrell, who brought in President Bush.

Neither of the two Democratic victors in the South ran against the war. Mr. Cazayoux’s view, set forth on his Web site, is markedly ambiguous compared to Mr. Obama’s, whose plan involves beginning a phased troop withdrawal immediately. Mr. Cazayoux’s Web site only pledges to support bringing the troops home “responsibly and with honor.”

Mr. Childers has said the war is not working, but Iraq appears nowhere on his Web site. Apparently, support for the war is still strong enough in Mississippi to prevent an anti-war Democrat from emphasizing that position.

It seems that what these victories teach is to be wary of conflating the strength of the Republican brand with that of conservative ideas. The former has clearly lost some of its power, but the latter are as strong as ever. And all successful political parties have to accommodate a wide political spectrum. Normally, this is accomplished by establishing a defining principle on which all party members can agree. We will see whether Mr. Obama, if he gains the nomination, can address this between the convention and November, but on the evidence of the special elections, he has yet to embrace the winning formula demonstrated in Louisiana and Mississippi.