Robert Johnson, on the job since 1989, will not be the Bronx district attorney much longer. It's only good news because his tenure has been so awful.

What's worse is that the party bosses were able to get rid of him only by offering him a cushy judgeship. The county's Democratic Party is expected to nominate him Thursdayfor a coveted spot as a state Supreme Court judge, a 14-year term.

The timing was rigged so Bronx voters will have no choice in picking Johnson's successor in a county with the city's worst record of convictions for violent felonies and the worst record for timely disposition of cases.

Here's how the scheme went down. Johnson, who had already formally accepted the Democratic, Republican and Conservative party nominations, and insisted he was running for re-election, had a sudden change of heart last week. "After much inner reflection, I have concluded that I would like to serve in another capacity . . . It is time for a change in my life," he said. Under the state's convoluted law, one way a candidate's name can be removed from the ballot is for the person to be nominated to another position also on the ballot in the upcoming election. (The other two ways are dying or moving away.)

And now who runs for DA? The hand-picked choice of the party bosses. No contested primary, no chance for a qualified outsider to step up and give the Bronx prosecutor's office the exorcism it needs. Instead, a party favorite will get the nod, someone who will make sure that all the jobs in the prosecutor's office remain patronage positions.

Assemb. Marcos Crespo, the new Bronx party chairman, defended the shady move by saying everybody does it. Sadly, he's right about that. It's a familiar path when any nominee gets in trouble and seems unelectable. These losers then go on the bench, which is one of the many problems with our system of electing judges in New York.

If Johnson wants a real change, he should try to do the honorable thing. Keep the nomination for district attorney, and then resign as soon as he is sworn in for a new term. That would allow for a special election, one that lets the voters decide.