THE MORNING PLUM:

A gunfight has erupted in the Democratic presidential primary. Over the weekend, the Hillary Clinton campaign escalated its attacks on Bernie Sanders over the Vermont Senator’s 2005 vote to shield gun manufacturers from liability, repeatedly calling on him to repudiate that vote.

But this battle, at bottom, is about more than guns. Clinton’s broadsides are, I believe, meant to feed into a broader dispute — one over who is more electable in a general election.

First, the details. As Bloomberg’s Jennifer Epstein reports, the Clinton campaign is now hitting Sanders for having voted to shield the gun industry from liability even though Sanders also voted against offering similar protections to a range of other industries, such as the fast food companies. “It makes zero sense to provide an exception for the gun industry,” top Clinton adviser John Podesta told Bloomberg. “Senator Sanders still refuses to admit he got it wrong.”

Clinton herself made similar comments to MSNBC. “When it really mattered, Senator Sanders voted with the gun lobby and I voted against the gun lobby,” she said. “Maybe it’s time for Senator Sanders to stand up and say, ‘I got this one wrong.’ But he hasn’t.”

Sanders defended himself extensively on ABC News yesterday, arguing that the legislation in question was complicated, that it might have implicated small gun shops for liability (which he wasn’t willing to do) and that he’d be willing to revisit the issue. But he stopped short of admitting his initial vote was wrong.

You’ll note that this skirmish is far removed from the policy area that has been most central to the battle between the two candidates — inequality and Wall Street reform. But in a way, the gun issue itself may be only part of the story here.

It’s my suspicion that it is not an accident that this gun battle comes at a moment when Clinton is also ramping up the argument that she is more electable in November. Clinton has released a tough new ad painting a dire picture of what will happen if Republicans win the White House, arguing: “Ask yourself: Who is the one candidate who can stop them? Hillary Clinton: Tested and tough.”

And so, the idea behind attacking Sanders on guns, in addition to the legit policy argument over the liability issue itself, also appears designed to throw Sanders on the defensive, and thus to illustrate which candidate really has the political fight to prevail in November. Sanders was indeed on the defensive during yesterday’s ABC interview.

This puts one in mind of Josh Marshall’s theory of how attack politics sometimes works, which holds that political attacks are often about something larger than the issues being disputed: they are also designed to send a “meta-message” that your opponent is too weak to hit back.  The Clinton camp has repeatedly called on Sanders to repudiate his previous vote. If he were to do that, it might reinforce such a meta-message.

None of this is meant to suggest that the issue itself isn’t important or that Clinton’s position on it is anything but sincere. And I could very well be wrong about this strategy — perhaps it couldn’t be further from the minds of Clinton strategists. But it’s worth entertaining as a possibility. And intended or not, this is the impact it may end up having on assessments of Sanders’ general election viability.

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 * TRUMP DOMINATES IN NEW HAMPSHIRE; CRUZ LEADS IOWA: New NBC/WSJ/Marist polls show that Ted Cruz leads Donald Trump among likely Iowa GOP caucus-goers by 28-24, with Marco Rubio at 13. Trump is way ahead among likely New Hampshire GOP primary voters, with 30 percent; meanwhile Marco Rubio, Cruz, Chris Christie and the others are bunched up in second place with far smaller vote shares.

A Trump victory in both states can’t be ruled out, and it’s looking increasingly possible that he’ll win one. Of course, the big unknown remains whether Trump’s supporters will show up.

* CLINTON AND SANDERS CLOSE IN IOWA, NEW HAMPSHIRE: The new NBC polls also find that Hillary Clinton leads Bernie Sanders among likely Iowa Democratic caucus-goers by 48-45, while Sanders leads Clinton by 50-46 among likely New Hampshire Dem primary voters.

The polling averages show a larger lead for Clinton in Iowa and a small lead for Sanders in New Hampshire. If Clinton just wins Iowa, she’ll have done what she needed to do. But if Sanders can somehow pull off a win in both, it could dramatically shift the later contests.

* CRUZ RULES OUT TRUMP-STYLE MASS DEPORTATIONS: On CNN’s State of the Union, Jake Tapper repeatedly asked Ted Cruz if he would support a “force” that goes “door to door” and rounds up the 11 million undocumented immigrants. He replied: “We have an enforcement force. It’s called Border Patrol and it’s called Immigration and Customs Enforcement.”

What this means is that Cruz is not vowing quite the proactive effort at mass deportations that Trump has promised. But he is still basically aligned with Trump on the issue: They both believe the right solution to the 11 million is to remove them.

He has sewn up endorsements of crucial Iowa evangelicals; deployed his pastor father, Rafael Cruz, as a surrogate; and activated networks of faith-driven voters….Mr. Cruz has pursued a national strategy of uniting evangelicals and other conservatives behind him, arguing that with the backing of energized conservatives alone he can win not only the nomination, but also the general election.

In other words, crucial to Cruz’s pitch to evangelicals is the story-line that an energized national army of them can propel their candidate into the White House.

Five of the Republican seats that Democrats are targeting are presidential battleground states that were won twice by Obama — New Hampshire, Wisconsin, Pennsylvania, Florida and Ohio. Strong enthusiasm for the Republican or Democratic nominee in any of those states could serve as much-needed coattails for Senate contenders.

Many of these contests could go the way of the presidential race in these states. It’s another reason senior Republicans have heartburn over the possibility of a Trump or Cruz nomination.

What did Mr. Obama do that was supposed to kill jobs? Quite a lot, actually. He signed the 2010 Dodd-Frank financial reform, which critics claimed would crush employment by starving businesses of capital. He raised taxes on high incomes, especially at the very top, where average tax rates rose by about six and a half percentage points after 2012, a step that critics claimed would destroy incentives. And he enacted a health reform that went into full effect in 2014, amid claims that it would have catastrophic effects on employment. Yet none of the dire predicted consequences of these policies have materialized.

But in the minds of many GOP base voters, of course, these dire predicted consequences have materialized. That’s the whole point!

President Obama, he said, wants “to fundamentally change America into a very different type of country,” and Rubio’s bill of particulars against the incumbent was long: He “doesn’t believe in free enterprise,” “looks with great suspicion at people with traditional values,” sees the Constitution as “a stale and outdated document” and views the United States as “an arrogant global power, a nation that needs to be cut down to size, that needs to be humbled.” We are now, Rubio said, echoing Trump, “a nation in decline.”

As I noted recently, Rubio’s sunny optimism is retreating behind a cloud of angry demagoguery, and the question is whether this risks squandering his most precious political asset.