The Democrats’ plan to jam through a late-session bill blocking future initiatives from appearing on primary election ballots is a sneaky, baldly partisan, pro-union measure.

Having said that, it’s not a bad idea.

Darrell Steinberg, the Democratic leader in the state Senate, admitted Monday that the party is “considering” a bill that would limit all initiative measures to future November general election ballots, beginning, not coincidentally, next year.

It isn’t meant as a good-government plan.

You see, pro-GOP types already are collecting signatures for an initiative that would ban unions from using members’ dues for political purposes and barring direct contributions from unions. Let’s call it “Son of Paycheck Protection,” a similar measure that as Prop. 75 failed in then-Gov. Arnold Schwarzenegger’s disastrous November 2005 special election.

Union officials are worried that if the new measure makes the June 2012 ballot, Republicans, looking at what’s likely to be a hard-fought and entertaining GOP primary election, are more likely to show up than Democrats who already know it’s going to be Obama, Take Two, come November.

But if that ballot measure with the union bull’s-eye was moved to November, when Democrats will be out in force …

That concern, when expressed by public employee unions who now give millions to Democratic causes every election year, is way more than a quiet suggestion to legislative leaders like Steinberg.

So while no bill has yet been introduced, expect to see some sort of legislative effort to help out the unions, especially one that can be passed by an all-Democrat, simple majority vote.

Not surprisingly, Republicans already are starting to howl. Fiddling with the initiative rules is “a pretty outrageous play,” that would toss more than 100 years of election tradition out the window, said former GOP state official Jon Fleischman on his FlashReport website.

But, strictly by accident, Democratic leaders have stumbled on a way to help reform the state’s tattered initiative process. Since initiatives are designed to make major changes that affect all Californians, what’s wrong with limiting them to the elections that attract the most voters?

Gaming the initiative system has a long and sordid history in California. There’s a reason PG&E scrambled to make sure its initiative to require a two-thirds vote in local elections for public power was on the June 2010 primary ballot (turnout: 33.3 percent) rather than on the November 2010 general election ballot (turnout: 59.5 percent).

Of course, as PG&E discovered about $46 million too late, low turnout is no guarantee of success for a special interest ballot measure, but more voters are always better when it comes to making decisions on initiatives.

It’s not as though limiting initiatives to the general election is unusual. Of the 24 states that allow ballot initiatives, only four – California, Alaska, North Dakota and Oklahoma – let them appear on primary in special election ballots.

Nevada, our next-door neighbor, requires two separate statewide votes on any initiative that would amend the state constitution before it takes effect.

That doesn’t mean the Democrats should get away with their game playing. If they do push across a bill to jigger the initiative rules for their allies in labor, Gov. Jerry Brown should veto it.

But he then should propose a straightforward measure that could go to the voters next June, asking simply whether all initiatives should be limited to the general election ballot.

The five-month delay between June and November isn’t going to bother any measure that’s not designed strictly for quick-hitting political mischief.

And it will be interesting to see who shows up to argue that less democracy is a good thing when it comes to voting on initiatives.

John Wildermuth is a long-time writer on California politics.