PITTSBURGH — Almost all the shibboleths of Washington conventional wisdom took a hit in Tuesday’s voting. Yet advocates of a single national political narrative clung to the difficulties of two incumbent Democratic senators to keep spinning the same old tale.

It’s true that the idea of incumbents and party establishments being in trouble won some support from the defeat of Sen. Arlen Specter in the Pennsylvania primary and Sen. Blanche Lincoln’s failure to avoid a runoff in Arkansas. But the races tell different stories.

Specter, a Republican-turned-Democrat who was defeated by Rep. Joe Sestak, could not survive what is so far the year’s best television advertisement. It linked footage of Specter saying he changed parties so he could get re-elected with video of President George W. Bush enthusiastically endorsing Specter in his previous Senate run.

The ad’s double whammy compactly summarized the gut reactions of Democrats against an incumbent backed by the party’s major figures, from President Obama to Gov. Ed Rendell. Democrats never trusted Specter, their foe for so long, and anti-Bush feeling remains a Democratic rallying cry that the party can still invoke to punch up turnout from core sympathizers this fall.

That Specter’s support collapsed so quickly everywhere outside Philadelphia suggested how weak he would likely have been against conservative Republican nominee Pat Toomey. Party leaders who backed Specter can nonetheless be relieved that voters picked the stronger candidate for November.

As for Lincoln, she was already the most vulnerable Senate Democratic incumbent. The late-starting campaign of Lt. Gov. Bill Halter took advantage of this weakness and forced the runoff. He married generalized protest voting with the specific gripes of liberal groups against Lincoln’s inconsistent record on issues such as union rights and health care.

Rand Paul claimed his upending of the Kentucky Republican establishment in the Senate primary as a triumph for the tea party. That it was. But the tea party has yet to prove that it is anything more than an inside-the-party right-wing protest movement. There is no evidence yet of its reach outside the GOP, but there was evidence on Tuesday that there are limits to the anti-government mood that is supposedly sweeping the country.

In Arizona — nobody’s idea of a liberal state — voters supported a temporary increase in the sales tax from 5.6 to 6.6 cents on the dollar, to raise $1 billion annually. This, coupled with a large tax increase on businesses and high-income earners endorsed by voters in Oregon earlier this year, suggests a pragmatic electorate that is far less reflexively opposed to taxes or government than tea party cheerleaders would have us believe.

The most significant result for the fall was the Democrats’ success in holding the western Pennsylvania House seat left vacant by the death of John Murtha. Democrat Mark Critz won an impressive nine-point victory over Republican Tim Burns by distancing himself from Obama and liberal positions on guns and abortion, but also by running a relentlessly economic populist message on jobs and outsourcing. He also promised to deliver federal largesse the way Murtha had.

Democrats will make even more of this result than is justified, given the area’s past Democratic history. But Pennsylvania’s 12th District is precisely the sort of seat Republicans will need to win this fall if they are to take over the House. It is, for example, the only district in the country that switched from Democrat John Kerry in 2004 to John McCain in 2008.

Yet even though Obama’s standing in the region is lower than it is nationwide, Burns’ rote Republican campaign against Obama and House Speaker Nancy Pelosi failed miserably. Democrats, in the meantime, believe they have found a formula to keep some of the more conservative districts they now hold.

Of the 56 seats the Democrats picked up from Republicans in either 2006 or 2008, 23 of them were carried by McCain; in six more, Obama was held to 51 percent or less. These are at the heart of Republican hopes and the reason why it will be hard for Republicans not to gain in the House this fall.

If Democrats can hang on to some of these McCain districts, they will not only keep control of the House but may be able to hold Republican gains to 25 seats or fewer. After the enormous buildup of Republican expectations, such a result would be a disappointment. That is why, paradoxically, Washington’s conventional wisdom of impending Democratic catastrophe is one of the best things Obama’s party has going for it.

E.J. Dionne’s e-mail address is ejdionne(at)washpost.com.

© 2010, Washington Post Writers Group

Your support is crucial…

With an uncertain future and a new administration casting doubt on press freedoms, the danger is clear: The truth is at risk.

Now is the time to give. Your tax-deductible support allows us to dig deeper, delivering fearless investigative reporting and analysis that exposes what’s really happening — without compromise.

Stand with our courageous journalists. Donate today to protect a free press, uphold democracy and unearth untold stories.

SUPPORT TRUTHDIG