Delaware's Republican voters will choose today between two think-alike Reagan conservatives who aspire to be the party's candidate for U.S. Senate.

The primary matches James H. Baxter Jr. 54, a downstate farmer-businessman and longtime party worker, against James A. Venema, 37, a manufacturer of cardboard signs, leader of the resistance to court-ordered school desegregation in Wilmington and a registered Independent until he declared his candidacy in March.

The winner gets to take on popular first-team incumbent Joseph R. Biden Jr., 35 - a task most political observers in the state rate little better than hopeless.

Baxter and Venema have found nothing of substance to disagree on in a tepid three-month campaign. If there is an issue, though, it is the intensity of their opposition to court-ordered busing, scheduled to begin in Wilmington and its suburbs two days after the primary.

"I've exhibited leadership abilities," Venema said, because he founded the Positve Action Committee, a group that opposes busing, and its counterpart, the National Association of Neighborhood Schools. Court-ordered desegregation is a powerful issue, he said, because it brings home to people the "increasing federal control of our lives."

Baxter also would support legislation to limit or preclude busing, but he has said "people (in Delaware) are reconciled to the fact that busing is here."

That sort of moderation has won Baxter the backing of what Venema calls "the Greenville element" - residents of Wilmington's wealthiest suburb who find Venema's activist opposition to busing a little scary.

Baxter easily won the party's endorsement at a June convention and has raised $50,000 for the first leg of the race, about twice what his opponents managed. Venema, though, has the backing of 13 of 14 suburban Republican legislators, who think he would be the stronger candidate against Biden.

The two men do offer very different backgrounds and personal styles.

Baxter lives less than a mile from where he was born in the crossroads town of Stockey. He began farming on 10 acres in 1941 and has built a prospering business that turns out a half-million broiler chickens a year, plus corn, barley and soybeans grown on more than 2,000 acres.

He starts campaign speeches with a joke about an outhouse and then says, in his soft-spoken, halting speaking style, "We've got to quit feeding those big spenders down in Washington."

Venema, a native of Michigan and one-time economics instructor, is the more aggressive and articulate sermonizer against federal deficits - though some Republican leaders have recommended he soften his image.

Venema's cardboard sign company, Delmic Display, sells multicolored signs with changeable lettering - mainly to bowling alleys. In the early 1970s, he was a representative for Glenn Turner's Koscot Interplanetary cosmetic company.

Venema barely recouped a $29,000 investment, he said, and escaped legal trouble himself when Turner's pyramid sales scheme collapsed. "Some people have skeletons in their closet," he has joked, "I have cosmetics."

Until this year, Delaware had a aide split between two candidates. The new law has brought no rush of candidates, though.

Biden is unopposed.Also having walk-throughs to the general electiodn are the two candidates for Delaware's only seat in the U.S. House of Representatives - incumbent Republican Thomas B. Evans Jr., 48, and Democrat Gary B. Hines, 27, a former newspaper reporter and political aide.