A rickety train, crammed with more than 400 Gary Hart supporters, inched along rusty tracks toward Wilkes-Barre. The unheated cars swayed and creaked as a 1923-model steam engine tugged them alongside the flood-swollen Susquehanna River. Near the end of the trip, the train had to slow to 10 miles an hour because of the poor roadbed.
This was a symbolic journey for Senator Hart, who is hoping to rebound in today's Pennsylvania presidential primary. The ride aboard the outdated train demonstrated much of what the senator has been saying about America's ability to compete and create the jobs it needs.
In the short run, Hart is pushing a 15-year program to rebuild America's crumbling infrastructure - its railroads, highways, bridges, and water and sewer systems. In the long run he is proposing new ways to revitalize American industry. He would experiment. He would attempt to harness high technology to save old-line industries. He would use new avenues of investment to keep America at the forefront of new industries like computers and robots.
Despite such ''new ideas'' from Hart, however, it is Walter Mondale who may benefit most from any economic debate that has taken place in Pennsylvania in recent days. Mr. Mondale, unlike Hart, isn't plumping for ground-breaking ideas. His approach is more traditional - a blend of New Deal, Fair Deal, and other Democratic programs, updated for the 1980s.
Thus, while Hart talks about sweeping plans to restructure the auto and steel industries, Mondale picks up points for his ad hoc role in saving the Chrysler Corporation when it was about to go bankrupt a few years ago. Hart voted against helping Chrysler.
While Mondale talks about things everybody can understand - like reducing the federal deficit - Hart's ''new ideas'' often fail to inspire political excitement. An example: his frequent calls for individual training accounts, which, in his words, ''would supplement the current program of unemployment insurance and give workers control over their own futures.''
The political stump, perhaps, is one of the worst places to discuss economic ideas. Crowds look for words to cheer, not for complicated economic theory.
Hart, however, keeps trying. He has focused on economic policy perhaps as dutifully and enthusiastically as any Democrat in the Senate.
One reason is that Hart says he believes that basic Democratic policy needs updating. Back in the years of Harry Truman, John Kennedy, and Lyndon Johnson, he notes, the growing United States economy could pay for all kinds of new social programs. Democrats won election after election by promising to divide up that expanding economic pie with various constituencies.
Then came ''stagflation'' - the 1970s problem of inflation with little or no growth. Real wages stopped rising. A backlash developed among middle-class voters, who resented bigger federal benefits for some Americans while they were socked with ever higher taxes to pay for them.
Hart was one of the first Democrats to decide that his party must not only concern itself with social justice, but also with the problem of ''making the pie grow.'' He began to focus, along with other young senators such as Paul E. Tsongas of Massachusetts, on ways to make this happen. This, he explains, is why he voted against the Chrysler bailout. Helping Chrysler was a ''band-aid'' approach to America's problems, and failed to meet fundamental problems that brought about Chrysler's predicament.
Thus Hart has developed (sometimes tentatively) a mixed bag of policies to meet today's challenges. Those policies include several key points:
1. A mammoth public-works project - including railroads and highways - to put people back to work quickly. The program would cost billions and would use funds saved by canceling the B-1B bomber program and the MX missile.
2. A huge investment in education, ''so a high school diploma is more than an admission to the unemployment line.'' This is a long-term project to make a major national commitment to develop what Hart calls ''human capital,'' the country's most important resource.
3. A long-term program to revitalize old industries, such as steel and autos, that play a central role in US defense. To save and invigorate such companies, Hart sees Washington playing a role in planning and bringing business and labor together. He also supports certain subsidies, such as loan guarantees, to help these industries. But such help must be tied to making these industries more competitive, and keeping jobs at home.
4. Small, high-risk companies - such as Apple and Atari - are a major source of new jobs and technological leadership. Hart would ease government rules that now require that pension funds, for example, be invested conservatively. Such rules prevent these funds from going into these high-growth (and high-risk) areas.
To control inflation as the economy speeds up, Hart also has shown an interest in setting wage-and-price guidelines. These might be enforced with tax penalties on companies that exceed them.
The Mondale approach is more traditional. He says it involves ''five key steps.'' These include: Reduce the deficit, strengthen exports, increase investment, fight inflation, and assist both workers and business.
Central to everything in the Mondale program is cutting the deficit. He would do this by: (1) boosting defense spending at a slower pace than President Reagan (''terminate the B-1 bomber, reject the MX''); (2) controlling medicare costs (''I will tell the medical establishment, 'Enough is enough' ''); (3) moderating farm subsidies by bringing production in line with demand and increasing exports; (4) boosting federal revenues by repealing indexing and raising corporate taxes; and (5) coordinating fiscal and monetary policies better.
Both candidates talk frequently about greater cooperation among business, labor, and government. That's the only way, they say, that America can meet today's tough foreign competition.