Republican presidential candidate Bob Dole decided yesterday not to enter the presidential primary in his home state of Kansas. Friends said Dole was afraid a poor showing in his home primary would undermine his chances to be reelected to the Senate this year.

Dole, who was campaigning in New Hampshire yesterday, released a statement saying he was not yet ready to withdraw from the presidential sweepstakes. But he said his duties as a senator will "continue to be my first priority."

Dole, the Republican vice-presidential candidate in 1976, ran last among the Republican presidential hopefuls in last month's Iowa caucuses, and he ranks at the bottom of the major GOP candidates in most opinion polls. Accordingly, friends in Kansas have been urging him to give up his presidential bid so he can concentrate on winning a third Senate term.

"A lot of his friends have been telling him it's time to stop mickey-mousing around with this thing," said McDill (Huck) Boyd, the Republican national committeeman from Kansas and a longtime Dole adviser.

"If he wants to gallop back to New Hampshire and try his luck a little more, you just have to strike that up to his tenacious streak. But after that, we want him to stop the president business and concentrate on getting back to the Senate."

It seemed that Dole had taken that advice at noon yesterday when the filing deadline for Kansas' April 1 presidential primary passed with no entry from Dole. Nineteen other candidates, including all the major contenders in both parties, did file on time.

But Dole, an intense 56-year-old whose campaign speeches generally contain as many jokes as a Johnny Carson monologue, left open the possibility yesterday that he would stay in the presidential contest if he does well in upcoming primaries in New England and the South over the next two months.

"If I do well between now and April 1, I believe I can prevail without being on the Kansas primary ballot," Dole's statement said.

Write-in ballots will not be legal in the Kansas primary, but there will be an "uncommitted" slate on the ballot, so Dole could presumably ask his home-state supporters to vote "uncommitted" as a sign of support for him.

But Boyd, the national committeeman, said yesterday he hoped Dole would not try anything like that. "We want him to turn his friends loose so they can start bragging about his Senate career and they don't have to worry about the presidential primary," Boyd said.

Dole has until June 20 to file as a candidate for reelection to the Senate.