DES MOINES -- With Vice President Bush solidifying his lead over Sen. Robert J. Dole (Kan.) among the two core groups of the Republican Party, the GOP has good prospects of reassembling the coalition that gave Ronald Reagan two presidential victories, according to a national Gallup Poll released here Wednesday by the Times Mirror publishing company.

The survey, based on in-depth interviews with 2,109 people Jan. 8-19, showed Democrats heading toward a potential collision between their New Deal constituency and younger, more independent party members .

At this point, before the first direct voter test of candidates in Iowa Monday, "the Republicans are a lot closer to putting together the old Reagan coalition than the Democrats are to putting together any coalition," said Andrew Kohut, president of the Gallup organization.

The Times Mirror survey differs from standard polls in classifying all voters by their fundamental values, rather than by age, sex, race, geography or ideology.

The January poll found very large majorities -- of from 64 percent to 91 percent -- of three core Reagan constituencies called "enterprisers, moralists and upbeats" saying they were likely to support Bush or Dole against any Democrat next November.

By contrast, it was rare for as much as 50 percent of any of the core Democratic groups -- identified as "New Dealers, '60s Democrats, passive poor or partisan poor" -- to have that degree of commitment to any of the seven Democratic contenders.

Bush leads Dole, 45 percent to 23 percent, among Republicans and Republican-leaning independents, the survey said.

Bush has expanded his lead among "enterprisers," an affluent, educated Republican-leaning group, since last spring's survey, Kohut said, largely because that group has increasing confidence in Reagan and sees Bush as continuing Reagan's policies.

Bush also leads Dole among "moralists," the other big Republican bloc, and even among those who disapprove of Reagan. Those voters explain Bush's big lead in many surveys of the southern states involved in primary elections on "Super Tuesday," March 8.

Dole's best hope, Kohut said, is to focus the race on a personal contrast with Bush. Dole receives higher marks for being strong, getting things done, being honest and ethical and having a fresh approach.

By contrast, the largest single Democratic bloc, the older, blue-collar voters called "New Dealers," are "up for grabs," Kohut said, with one-third undecided and one-third for former senator Gary Hart (Colo.).

Massachusetts Gov. Michael S. Dukakis leads among younger

" '60s Democrats" and "seculars," but Kohut suggested that his two major rivals in Iowa, Rep. Richard A. Gephardt (Mo.) and Sen. Paul Simon (Ill.) may have raised issues with a greater potential appeal to the "New Dealers," a particularly significant voting bloc in the South.