Her plan to increase federal investment in infrastructure is a particularly good idea, approved by most economists, labor unions and even the Chamber of Commerce. It would not just lift employment but provide decent wages to those who need them most. Infrastructure occupations often pay up to 30 percent more than other jobs to workers with a high school diploma or less.

With interest rates near zero, infrastructure amounts to a slam-dunk investment opportunity. Continuing to defer the maintenance of America’s crumbling highways and water systems will certainly be more costly than fixing them now.

Still, there is something anachronistic about Mrs. Clinton’s focus.

“I am really, totally committed to bringing back manufacturing” sounds great in Youngstown, Ohio, ahead of the state’s primary. But it is not a policy to revive a struggling working class. There are only 300,000 steel workers in the United States. How many can be added by threatening to slap anti-dumping tariffs on imports of Chinese steel? Not many.

Her turn against the trans-Pacific trade agreement with Asian countries — a deal she once supported — makes sense within her overall strategy. Why waste time and political capital on an agreement that might make the economy more efficient but will not create lots of jobs? Still, this does not amount to a strategy about global trade.

To be sure, Mrs. Clinton has been pushed to some of these positions by Donald Trump and Bernie Sanders. Their show of force in politically crucial Rust Belt states underscored how important it was to strike a pro-manufacturing, trade-hostile stance.

And yet Mrs. Clinton’s careful collection of tweaks and prods is no match for the challenge.

For instance, she is proposing $275 billion in federal infrastructure investment over five years. That is less than 10 percent of what the American Society of Civil Engineers estimates will be needed.

Mrs. Clinton’s entire tax plan would raise only $1.1 trillion over the next decade, according to the Tax Policy Center, half a percentage point of the nation’s gross domestic product.