CLINTON WEIGHS VISIT TO NORTHERN IRELAND.(MAIN)

Byline: STEWART M. POWELL Times Union Washington bureau

WASHINGTON -- President Clinton is considering a visit to Northern Ireland to campaign for ratification of the historic peace agreement brokered by his envoy, former Sen. George Mitchell.

Clinton told Mitchell at the White House Monday that he would campaign for the peace pact before a May 22 referendum in Northern Ireland and the Republic of Ireland on the agreement if he thought it would help.

``I'm always willing to do whatever I can to help but I don't want to do something to undermine the chances of success,'' he said.

Clinton said he would consult with British Prime Minister Tony …