New York — A red emergency telephone appears on the TV screen. In the background, a somber male voice says: ''The most awesome, powerful responsibility in the world lies in the hand that picks up this phone. The idea of an unsure, unsteady, untested hand is something to really think about. This is the issue of our times.''
Over and over in New York, Walter Mondale has paid to have this advertisement run on television. The ''unsure, unsteady, untested hand,'' of course, is supposed to belong to Gary Hart. And the charge makes Hart supporters fume.
Thirty-second TV ads have become a focal point of the Democratic presidential race. Each side charges the other is going too far, becoming too personal.
The Mondale campaign has been pouring between $300,000 and $400,000 into its TV effort here in the past two weeks, mostly in the costly New York City market. Hart forces have spent about $1 million here.
Some political experts say there is a danger that the charges and countercharges flying back and forth on TV could divide the party and cripple its chances against Ronald Reagan. There's little doubt that the Republicans are collecting an arsenal of ammunition for use this fall.
The anger on both sides is more than just the usual political brouhaha. Each side has managed to really ruffle the other's feathers. Says political scientist Norman Ornstein:
''I was struck in the CBS debate (last week in New York City) with the degree of obvious indignation shown by both Mondale and Hart. It wasn't the kind of put-on indignation that we saw earlier between John Glenn and Mondale. . . . This time they really do take it seriously.''
One of the things that has angered Mr. Mondale has been the Hart ad known as ''Central America.'' On the screen, viewers see a burning fuse, apparently leading to a bomb. As the fuse crackles, an announcer says:
''When President Reagan sent our troops to Central America, he called them advisers. Remember Vietnam? Our troops now serve as bodyguards to dictators, and are a slow-burning fuse to war.''
The voice continues:
''Vice-President Mondale agrees with President Reagan, and said he, too, would leave some of the troops there as bargaining chips with Nicaragua. And he attacks Gary Hart for forcefully saying, Get them out!
''Our sons as bargaining chips - will we never learn?''
This ad makes Mondale sizzle. In last week's debate, he challenged Senator Hart about it, saying:
''Why do you run those ads suggesting that I'm out trying to kill kids, when you know better?''
Mondale is also peeved that Hart continues to put him on the ''wrong'' side of the Vietnam issue with the charge that he was late in opposing the war.
The Mondale and Hart ads are the products of two very different agencies. Mondale's TV commercials come from the posh Fifth Avenue ad shop of political veteran David Garth. Hart's are the product of a newcomer to Washington, Raymond Strother, who hails from Texas and Louisiana.
The Vietnam references in the Strother ads are no surprise. Hart, after all, was campaign manager for George McGovern, who ran a one-issue campaign based on Vietnam back in 1972. And Mr. Strother can empathize with Hart's feelings. Strother's brother was killed in Vietnam.
Strother says that while Hart's ads may sting Mondale, it is Mondale's ads that have really gotten personal. They not only use Hart's name but question his personal ability to do the job, as in the ''red phone'' ad.
Hart's ads, on the other hand, focus primarily on issues, which is the way Hart wants them, Strothers says. The Central America ad, for example, was based on Mondale's speech on March 14 before the Chicago Council on Foreign Relations, says Strother.
In that speech, Mondale said he would leave some US troops in Honduras while he sought to remove Cuban forces in the region. Thus the use of the phrase ''bargaining chips'' in the Hart ad.
''Mondale's ads are very tough on Hart,'' Strother says. ''We've tried to be very restrained. Hart is very reluctant to be negative. In fact, he rejects a lot of ads written by me and by his pollsters.'' Strother says that if he got his way, Hart's ads would be ''a little harder hitting, with more of an edge to them, and more personal.''
Political scientist Ornstein expects to see the attacks by both Mondale and Hart diffused a little bit in coming weeks. The New York primary was so important to both candidates, especially Mondale, that it pushed both campaigns to the edge.
Even so, Dr. Ornstein does not think any irreparable damage has been done to the Democrats. He points out that in 1960 a bitter struggle broke out between John F. Kennedy and Lyndon B. Johnson, and that ended with a ''marriage of convenience'' that carried the Democrats right into the White House.
If JFK and LBJ could work things out, Ornstein suggests, there's little reason to think that WFM and GWH can't do the same thing.