Vice President Bush has built a strong lead over Sen. Robert J. Dole (R-Kan.) in the Republican presidential nomination race because of his links to President Reagan, his broad experience and his perceived capacity to deal with foreign countries, the latest Washington Post-ABC News poll indicates.

Bush's 49-to-26 percent lead over Dole among Republicans in the survey rests on his overwhelming strength among those who admire Reagan, especially young voters. Republicans who think Reagan has an unstated preference almost unanimously believe Bush is his choice.

So far, Dole is not being helped in his quest for the nomination by evidence that he may be a stronger general-election candidate. Democrats give him better ratings than Bush on economic and budget issues, strength of leadership and sympathy for the problems of the average person.

The survey strongly suggests that as far as Republican primaries are concerned, Bush is benefiting by stressing his loyalty to Reagan, while Dole's themes of leadership and humble origins may have more appeal to Democratic crossovers in the general election.

This national survey contrasts with a series of recent polls in Iowa, showing Dole ahead in the first caucuses on Feb. 8. In previous years, national polls have been reshuffled by each round of caucus and primary results.

The study of 507 registered Republicans and Republican-leaning independents, completed Saturday, pinpointed one potential threat to Bush. His lead rests largely on young and middle-aged voters, less likely, history says, to participate in primaries and caucuses than older voters. Bush has an 8-to-1 lead among those between 18 and 30 and a 2-to-1 lead among those between 31 and 44. Among those over 45, his margin shrinks to 4 points.

His edge over Dole is only 14 points in the Midwest, where several early contests will be held, but balloons to twice that size in the other three sections of the country.

Despite those potential dangers, Eddie Mahe, an experienced Republican campaign consultant who is not working for any of the GOP contenders, said the findings of the poll "tell me that unless something happens to shake the process and skew turnout, George Bush is our nominee. It's going to be real difficult for Bob Dole to overcome some of these numbers."

Mahe said he was particularly impressed by results of a battery of questions asking voters to rate Bush and Dole in several dimensions of leadership. Among Republicans, Bush had a 57-point advantage on having the background and experience to be president; a 42-point advantage on handling relations with other countries, and a 21-point advantage on being less likely to raise taxes. He had much smaller margins on doing what is right, even if it hurt him politically, and assuring that the government operates efficiently. On two questions -- strength of leadership and understanding the problems of the average person -- Dole and Bush were essentially even among Republicans.

Mahe called these findings "leading indicators" of the likely results in the upcoming GOP primaries.

Ironically, Democrats in the survey often expressed almost mirror-image judgments on Bush and Dole, rating the Kansas senator superior in every category except background and experience, often by margins of more than 20 points. Because of that strength among Democrats, Dole had better overall approval-disapproval scores than Bush: 45-21 for Dole, 49-37 for Bush. But among Republicans only, Bush was plus 50, Dole plus 43.

Among Democrats, Dole was plus 24, Bush minus 14. Mahe commented that such a gap would undoubtedly make it easier for Dole than Bush to frame a successful general-election strategy, "but I don't think that translates to making a difference in the primary process."

The survey showed a close correlation between support for Reagan and support for Bush. Four of every five Republicans approve of Reagan's performance as president, and among them, Bush leads Dole 2 to 1. Among the one-fifth who disapprove of Reagan, Dole runs within 8 points of Bush.

Mahe said that Dole "is in an almost impossible box" with regard to the Reagan-Bush connection. "The more people dislike Reagan, the better chance he has, but he cannot run against Reagan. And the more he does to praise and support Reagan, the more he helps George Bush."

Polling editor Richard Morin and polling analyst Kenneth E. John contributed to this report.