Massachusetts Gov. Michael S. Dukakis holds a substantial lead among likely voters in New Hampshire's Democratic primary, according to a Boston Globe poll. The poll shows that Dukakis' lead over former Colorado senator Gary Hart has increased since Hart reentered the contest on Dec. 15.

The telephone poll of 545 likely Democratic voters indicates that the race is: Dukakis, 40 percent; Hart, 18 percent; Sen. Paul Simon (D-Ill.), 14 percent; Jesse L. Jackson, 9 percent; Rep. Richard A. Gephardt (D-Mo.) and Sen. Albert Gore Jr. (D-Tenn.), 3 percent each; former Arizona governor Bruce Babbitt, 2 percent; 11 percent undecided.

Sixty-nine percent of New Hampshire Democrats view Dukakis favorably, a figure significantly higher than that for any other Democratic candidate. Fully one-third of Democratic voters polled (34 percent) say their opinion of Hart has declined during the campaign, and the same number view him "very unfavorably." Simon seems to be the Democrat with the greatest potential to grow in support, the poll indicated.

On the Republican side, Bush is in a strong position to win in New Hampshire, but Dole presents a serious challenge, according to the poll. When 612 likely Republican primary voters were asked for whom they would vote now, the race stacked up this way: Bush, 42 percent; Dole, 23 percent; Rep. Jack Kemp (R-N.Y.), 10 percent; former Delaware governor Pierre S. (Pete) du Pont IV, 7 percent; Pat Robertson, 6 percent; Alexander M. Haig Jr., 4 percent; 9 percent undecided. The poll was taken by telephone Dec. 17-23.