Michael Dukakis took his wife home from the hospital, met with Costa Rican President Oscar Arias and got back to work at the Massachusetts Statehouse Thursday in his first day back in Boston after sewing up the Democratic presidential nomination.

His presidential campaign focused on choosing a running mate.Vice President George Bush, the all-but-certain Republican nominee, was opening his post-primary campaign with a trip to Texas, grateful for new words of support from President Reagan who said Wednesday he would do "everything I can" to help Bush win.

Dukakis, who has strongly criticized Reagan administration policies in Latin America, praised Arias' peace plan for Central America and said the United States must "develop a new relationship based on respect" with the region's areas.

Arias sidestepped a question about the U.S. elections, saying only that he would be a "good friend of whoever you decide to elect."

Dukakis then went to the hospital where his wife Kitty was released six days after undergoing spinal surgery.

Dukakis, whose victories in the final four primaries of the season on Tuesday gave him the delegates he needs for a first-ballot victory at the convention, received a round of support from one-time opponents on Wednesday.

Rep. Richard Gephardt, Sen. Paul Simon and former Arizona Gov. Bruce Babbitt all weighed in with endorsements Wednesday. And New York Gov. Mario Cuomo, the most speculated-about non-candidate of the year, finally lent his backing.