Ronald Reagan and George Bush carried their final appeals to Pennsylvania voters today, on the eve of a primary that could shut the door on the last remaining challenge to Reagan's capture of the Republican presidential nomination.

While Bush wound up an exhaustive, million-dollar effort to keep the flickering flame of his candidacy alive, stumping Philadelphia and its suburbs, Reagan crossed Pennsylvania from east to west, saying the fight is over and he has won.

Reagan was joined by the latest former rival to board his bandwagon, Sen. Howard H. Baker Jr. (R-Tenn.). Baker said in Wilkes-Barre: "This is a time to march together with a man who will be a historic president -- Ronald Reagan."

Reagan told reporters at the start of a final swing that also included stops in Lancaster and the Pittsburgh blue-collar suburb, Coraopolis, that a victory over Bush Tuesday could be the end of the nomination battle.

Asked if he thought Bush should cash in his chips if he loses here, Reagan said, "If I was in his same position at this stage, I'd have to give serious consideration to that possibility . . . The odds are very much against him now."

Going into the Pennsylvania voting, Reagan has 528 of the 998 delegates needed for nomination, compared to 96 for Bush and 56 for Rep. John B. Anderson.Anderson, who is expected to end his quest for the GOP nomination and announce as an independent candidate for president later this week, is not on the Pennsylvania ballot.

Pennsylvania Republicans will elect 77 district delegates who, along with the six at-large delegates (the governor, two senators and three party officials), will make up the fourth-largest voting bloc at the party's national convention in Detroit this July.

While all the delegates are officially uncommitted, Reagan's state chairman, Drew Lewis, said the endorsements of powerful local organizations in Philadelphia and some of its suburbs, plus the familiarity of some Reagan supporters' names, virtually guarantee the former California governor will have at least 50 and probably as many as 55 of the delegates.

The Bush campaign -- less well organized here than in other states -- is fielding fewer and generally less-well-known delegates. A snafu over the identification of delegates and their districts in a Bush mailing last week further diminished the chances of a strong Bush showing in that part of the primary.

The former congressman and anbassador has concentrated 14 days of campaigning and a massive television blitz on winning the separate "beauty contest" -- a nonbinding presidential preference vote, which has no direct effect on the delegate election.

Bush's media campaign -- keyed to televised, prime-time, half-hour "Ask George Bush" town meetings -- has brought a sharp increase in affirmative responses to his telephone canvass. It has worried the Reagan campaign, which is being outspent by a factor of three or four to one.

"He's been here for weeks, and he's spent almost a million dollars," Reagan said today. "If you believe in advertising, you have to believe it will make a difference."

But Reagan has countered with a week of well-timed announcements of support from Republican leaders from neighboring New York, New Jersey, Delaware and Ohio -- all carrying the message to Pennsylvania Republicans that the nomination has been decided and a vote for Bush is a wasted gesture.

Lewis, who appeared more optimistic in recent days about Reagan's winning the "beauty contest," said today, "I think it's going to be very close, but my gut tells me we're going to win a squeaker."

Bush did not ease up on the final day of this campaign, in which he has been speaking more effectively than at any point since he became a candidate. In an appearance at Vilanova University, he accused Reagan of offering "simplistic solutions" to serious problems, and drew his loudest cheers by criticizing the "blunders" of the Carter administration.