In two weeks voters will go to the polls in a race that looks increasingly dire for Democrats. It’s not that voters agree with Republicans on the issues. On the contrary, polls show that a majority of voters across the political spectrum agree with core Democratic principles and programs.

The problem is that Republicans keep changing the subject, and Democrats keep letting them. Rather than letting themselves be kept on the defensive – about President Obama, the Affordable Care Act, Ebola, or the Middle East – Democrats would be wise to pick one or two key issues and keep hammering away at them.The Democrats should be using Social Security expansion as a key part of their 2014 election strategy. (See “Democrats Can Win on Social Security – By Fighting to Increase It.”)

A few of them have, and in recent days Social Security has been raised in several more Democratic races.

But the days are dwindling down to a precious few. There isn’t enough time left to promote Social Security expansion in depth, but Democrats can still use it as a key campaign tool. Here are five reasons why they should:

1. Social Security is a “core value” – and a winning issue.
As Celinda Lake told me in a radio interview (available here), there is “overwhelming” support for expanding Social Security and taxing millionaires to do it. This support is present among voters of all political leanings, including self-identified Republicans and independents. Social Security is a “core value” for voters, and Lake described it to us as a “valence issue” – that is, an issue that is likely to sway their vote.

Her observations came from a study of likely voters, nationwide and in several key states, which she conducted for Social Security Works and the Center for Community Change. Voters were asked how they felt about “increasing Social Security benefits and paying for that increase by having wealthy Americans pay the same rate into Social Security as everybody else.”

• 90 percent of Democrats said they support the idea; 75 percent strongly supported it.
• 73 percent of independents support it; 55 percent strongly supported it.
• 73 percent of Republicans support it; 47 percent strongly supported it.
• 63 percent said they are more likely to vote for a member of Congress who votes to increase Social Security.
• 70 percent said they are less likely to vote for someone who votes to cut Social Security benefits.

These findings reinforce several earlier polls (compiled in PopulistMajority.org), such as the one that found that “87 percent of voters favor protecting Social Security and Medicare.

”When I asked why more Democrats weren’t embracing this idea, Lake answered, “I can’t imagine.”

2. It helped them win in 2006.
When the Democrats took back the House of Representatives in 2006, Social Security was a key part of that victory. President Bush and Congressional Republicans tried unsuccessfully to privatize the program in 2005, which proved to be deeply unpopular with voters. The memory of that attempt was fresh in voters’ minds when they went to the polls the following year.

That year the Democrats held a nearly 30-point advantage among voters who were asked, “Which party do you trust more on Social Security?” (Wall Street Journal/Lake Research Partners) Four years later, after the Obama White House began flirting with Social Security cuts through the Simpson/Bowles Deficit Commission, the Dems’ 28-point lead had become a 3-point deficit. Voters actually trusted Republicans more on the issue, if only by a slight margin.

The Democrats lost the House that year.

3. It’s a great way to distinguish themselves from Republicans.
Social Security is a “core value” among voters. It’s also a signature Democratic accomplishment, one that Republicans tried to dismantle less than a decade ago.Of course, few Republicans are foolish enough to boast of their anti-Social Security efforts in an election year. That’s why candidates like Louisiana’s Mary Landrieu and Mark Pryor of Arkansas have begun running attack ads highlighting their opponents’ support for cutting Medicare and raising the Social Security age to 70.

But attack ads alone probably won’t be enough. Social Security expansion draws a clear line of demarcation between privatization-friendly Republicans and Democrats who want to expand the social safety net at a time of diminishing prosperity for most Americans.

Alaska Sen. Mark Begich understands this. He was one of the first Democrats on the Hill to embrace Social Security expansion, and he’s making it a cornerstone of this year’s race. That’s an interesting choice, given that he faces an uphill battle in a decidedly red state. (Remember demi-governor Palin?)

The latest Senate candidate to embrace this approach is Iowa Senate candidate Bruce Braley. This week Braley came out with a plan to expand Social Security that tracks closely with Lake’s polling. In a new television ad, Braley says that his plan would “Make millionaires pay Social Security taxes on all of their earned income,” “keep Social Security strong,” and “increase monthly benefits.”

That tracks with proposals from senators Begich, Bernie Sanders, Tom Harkin, and Elizabeth Warren.

4, People don’t like getting shafted.
The American people understand that the raw deal they’ve been given includes the lousy service they’ve been getting from everyone, especially big businesses like the cable operators. They know that when you cut administrative costs, you’re taking a chunk out of their day – and sometimes out of the services to which they’re entitled.

Now, thanks to overzealous budget-cutting in Washington, even Social Security suffers from this private-sector syndrome. Its administrative costs are a fraction of those in the private sector, and they’re fully funded by Social Security contributions (that is, by you and me).

The number of backlogged disability cases is now approaching one million.

Nevertheless, Congress keeps cutting Social Security’s administrative budget. They’re closing field offices, which negatively affects people’s ability to receive timely attention – or even to receive the benefits to which they’re entitled. (We interviewed Witold Skwierczynski of the American Federation of Government Employees here about this and found his comments informative.)

They’re planning to continue these cuts, and perhaps even to close Social Security’s offices altogether in favor of an Internet-based system and outsourced “private partners.” (See “A ‘Secret Plan’ to Close Social Security Offices – and Outsource Its Work.”) These service cutbacks are being implemented even as Baby Boom retirements are beginning create an enormous additional demand for services.

Voters understand that cuts in Social Security’s operating budget deprive them of something they’ve been paying for throughout their working lives. The next phase of Social Security expansion should also call for expanding, not shrinking, Social Security’s administrative functions.

5. It changes the subject.
As we were saying, Republicans have been setting the agenda this year. Ebola. ISIS – they want to talk about anything except what they have in mind for the vast majority of Americans.

Instead of answering silly questions like “Did you vote for Obama?” Democrats could keep doing what Bruce Braley is now doing in Iowa. His new ad points to opponent Joni Ernst’s support for Social Security privatization and emphasized the riskiness of that approach. And the narrator in a new Louisiana ad says (in that grim “narrator” voice):

“When it comes to seniors, Congressman Bill Cassidy has a plan: Raise the retirement age for Social Security and Medicare to 70.”

It’s late in the campaign, and voters’ minds may already be pretty much made up. But it only makes sense to put Republicans on the defensive for supporting proposals that would hurt American families – and for contrasting that with proposals that would make things better for those families.

But if Democrats are going to do that, they better act now.