Dale Bumpers, the Arkansas senator and presidential aspirant, has a name that Ring Lardner should have given to a relief pitcher, but because Bumpers pretends he has not made up his mind to run, he is called Hamlet. Persons who call him that should remember that after a bit of waffling about whether to be or not be, Hamlet got cracking and went down fighting.

At 57, Bumpers is graying, stocky but trim, and as eager as only a former governor can be to be something more than 1 percent of one-half of the legislative branch. He also is like the little girl with the curl on her forehead.

When he is good he is very good. Defending constitutional propriety, he was the only southern senator who opposed limiting courts' jurisdiction in busing cases. He opposed limiting jurisdiction concerning school prayer. He opposed extension of the ERA ratifying deadline. When he is bad, well . . .

I have seen tangled arguments for cutting the defense budget, but some of Bumpers' arguments look like linguine. He considers this a salient question: what has the Soviet Union not done that it would have done if the Reagan administration had projected a smaller five-year defense increase?

Take a yellow pad--better make it legal size --and try to diagram Bumpers' thinking. Let's see, maybe it is: unless you can prove that the Soviet Union would have committed a specific action in 1981 or 1982 if Reagan had not made his projection of defense spending through 1988, then the spending is unjustified.

Bumpers makes much of the fact that the administration's fiscal 1984 budget anticipates only $295.6 billion in revenues from personal income taxes, and that is just $57 billion more than the defense request. What is absent from such arithmetical irrelevancies is any reference to what is relevant: the Soviet threat. But talk about that threat does not go down well at the cattle shows where candidates strut their stuff for a few minutes in front of Democratic activists who, when not gorged on chocolate mousse, drive the nomination process.

Bumpers is a natural, effortless orator and is a big hit at those shows, where his unexacting challenge is to speak more electrifyingly than his rivals. This is entirely a tribute to his style. His substance is orthodox liberalism. For 1982 he earned an 85 percent "correct" rating from Americans for Democratic Action. Congressional Quarterly says he opposed Reagan slightly more than Ted Kennedy did.

He does practice a mildly unorthodox candor when, with a wave of his hand, he dismisses, without disputing, arguments against the nuclear freeze, which he supports. When you argue that it is unclear--not least to freeze supporters--what the effect of a freeze would be (what modernization of forces would be permitted?), he suggests you are missing the point, that the freeze resolution is therapeutic, a vehicle for expressing popular "frustration" about life in the nuclear age.

He is one of just three senators (New Jersey's Bill Bradley and South Carolina's Fritz Hollings--both Democrats--are the others) who in 1981 voted for Reagan's budget cuts but against his tax cuts. Therefore Bumpers is in a strong position to criticize Reagan for selling an unrealistically "ouchless" program. In conversation about a positive Democratic agenda--some small supplement to the anti-Reagan talk-- he speaks with animation about energy and environmentalism, but he gives the distinct impression of improvising, of making it up as he goes along, of doing market research. He seems to be counting on his presence to cause his campaign to catch fire.

Being a southerner, Bumpers could have an advantage, if he still has a pulse, after Iowa and New Hampshire. Twelve southern states from Virginia to Texas will have 26 percent of the delegates--more than half the total needed to nominate--and five southern states are currently scheduled to elect delegates in the 11 days following New Hampshire.

On the other hand, as vice presidential nominee, Bumpers could give badly needed rhetorical zip to a Mondale or Glenn ticket, and could help solve the Democrats' southern problem. Since 1968 Democrats have won just 17 electoral votes in the West, while Republicans have won 377. The Democrats cannot allow the South to remain a second weak region.

Bumpers says, of course, that he is not interested in the vice presidency. But as a wit once said, the vice presidency is like the last cookie on the plate: everybody says he won't take it, but somebody always does.