To get a measure of just how toxic the political atmosphere is for Democrats, consider this: Incumbents are so wary of touting their records, they are largely ignoring Wall Street reform, the only broadly popular item among the party’s major legislative accomplishments.

Back in mid-July, with the bill on its way to President Obama’s desk, White House spokesman Robert Gibbs predicted the measure, and the near-unanimous Republican opposition to it, would become a defining issue on the trail. “I think this will be a vote that Democrats will talk about through November as a way of highlighting the choice that people will get to make in 2010,” he said.

Indeed, some Republicans were privately jittery about that prospect, believing Democrats had finally struck on a political winner by giving themselves an opportunity to boast about cracking down on Wall Street abuses. “We were nervous,” one GOP operative said. “We thought they could use this.”

But take a survey of the hundreds of political ads now flooding the airwaves, and you’ll have a tough time finding Democrats who voted for the package reminding voters of it in specific terms. A handful of exceptions prove the trend. In Washington state, where state Sen. Dino Rossi is trying to unseat Sen. Patty Murray, the Murray camp has produced a trio of ads attacking that the challenger for advocating repeal of the law.

In Ohio, freshman Democratic Rep. Mary Jo Kilroy has put together a pair of ads trumpeting how she “stood up to the banks” and “took on Wall Street.”

Plenty of other candidates — incumbents and challengers, Democrats and Republicans — are tussling for the mantle of Wall Street reformer. But their ads either deal with the issue obliquely or focus on other finance-related votes, usually on the Troubled Asset Relief Program.

Why mum’s the word, from both parties

So what happened? Interviews with party strategists suggest that sometime between the triumphant mid-summer signing ceremony for the bill and the thick of an ugly campaign season, a new consensus emerged about the best tack for Democrats. Yes, the bill is popular. But, this thinking goes, incumbents lose more than they gain by highlighting it because the rest of their records are so unpopular, and any talk of what they did in Washington only reminds voters of that.

Senate Democrats got that specific advice from top-tier consultants before heading back out for the final stretch of campaigning this month. And in the House, “there’s an overall fear running through the Caucus that the more you talk about what you did in Washington, the easier it’s going to be for your opponent to tie you to Washington,” one Democratic leadership aide said.

Instead, endangered Democratic incumbents are focusing on votes they cast against the national party leadership on the stimulus package, the bank and auto industry bailouts, and the climate change and health care overhauls. And they are investing in defining their Republican opponents with negative personal attacks — “decisions they made on taxes or business deals,” one Democrat said, “because the issue agenda is just not with us right now.”

The effect is an odd silence in the campaign air wars around the financial reform package, a pillar of the Democratic agenda. While Democratic candidates largely ignore their own party’s success in passing the measure, Republicans are remaining similarly mum about it in a nod to the tricky politics of their position. The House Republican’s governing proposal, dubbed “The Pledge to America,” dedicates an entire section to the GOP’s plan to “repeal and replace” the health care overhaul, for example. But it is silent on the issue of the financial reform bill. Indeed, the words “Wall Street” and “banks” never even appear in the document.

Vice President Joe Biden, who’s been barnstorming the country trying to limit Democratic losses, defended the party’s strategy earlier this week. In an interview with Bloomberg, he listed the regulatory reform bill along with the health care package and the stimulus as measures Democrats aren’t campaigning on because, “it’s just too hard to explain.”

Lauren Weiner, a spokeswoman for Americans for Financial Reform, a coalition group backing the bill, acknowledged that while voters overwhelmingly blame banks for precipitating the recession, it’s tougher to explain how the Wall Street reform bill will get average workers back on the job. “We’re working on it,” she said.

Some Democrats think the party is missing a ripe line of attack. “It’s hard for me to understand why Democrats are not taking advantage of the issue, because it tests exceptionally well,” Democratic pollster Peter Hart said. Those defending seats are right not to run on their incumbency, he said, “but you can’t run from your label… When you have something you’ve done right and it’s popular, it seems to me you stress that point because you know you’re going to get beat up on cap-and-trade, and you know you’re going to get beat up on health care. So what’s your rejoinder? ‘I haven’t been there’?”