Democrats aiming for convention harmony reached agreements on party rules and a presidential campaign platform, but Jesse Jackson dismissed the platform document as "bland" - and predicted a floor fight or two.

Republican George Bush, for his part, said he and Democrat Michael Dukakis have serious foreign policy differences, singling out defense issues as a key battleground for the coming months.Meanwhile, a Gallup poll released Monday suggested that Dukakis holds a 13-point lead over Bush, 53 percent to 40 percent, with 7 percent undecided. That is in line with a string of surveys putting Dukakis' edge in double digits.

But the poll, conducted for the Times-Mirror Corp., also indicated that Dukakis' strength stemmed more from voters' negative feelings about Bush than positive feelings about the Democratic nominee-to-be.

"Dukakis is still a blank page to most people," said Andrew Kohut, president of the Gallup organization.

The survey, based on interviews with 3,021 adults from May 13-22, had a margin of error of 2 percentage points.

Dukakis was wrapping up a four-day vacation Monday before heading out on a campaign trip to the Midwest. The Massachusetts governor was flying home from Nantucket Monday night.

Dukakis tried to keep his island sojourn nearly free of campaign business. Press secretary Mark Gearan said Sunday the governor had not even talked by telephone with aides in Denver, where platform drafters were at work on a campaign manifesto.

The document that emerged conformed more closely to the wishes of the Dukakis camp than Jackson forces.

Jackson's calls for raising taxes on the rich, freezing the Pentagon budget, pledging no first use of nuclear weapons and supporting a Palestinian homeland were all turned aside.

"There will no doubt be some minority positions taken to the floor," Jackson said, but he refused to specify which issues he was referring to.

The Jackson forces did get their way on some platform matters, including a call for South Africa to be declared a terrorist state.

And Democratic rule-makers, meeting Saturday in Washington, agreed to an overhaul of party rules - which Jackson hailed as a "victory for the people. . . . a victory for democracy."