Sen. Bob Dole (R.-Kan.) declared yesterday that his Republican presidential campaign is not over, despite indications of a big Illinois victory for Vice President George Bush, but Sen. Paul Simon (D.-Ill.) admitted, "I have no plans beyond tomorrow"--and the home-state primary he needs to win.

With five presidential candidates racing around the state in a final day of campaigning, the Rev. Jesse Jackson was buoyed by a poll suggesting he may have pulled even with fellow favorite son Simon.

"On the eve of a significant breakthrough...with your help, we, the people, can win Illinois," Jackson told a cheering crowd of about 1800 in Carbondale.

Massachusetts Gov. Michael S. Dukakis, placing third, sought a good enough showing to keep up some momentum from Super Tuesday. Over and over yesterday, Dukakis hammered at Simon's prediction of a deadlock at the Democratic convention.

It "would be a disaster" for the Democrats to end the primary process without a clear frontrunner, Dukakis said, with "negotiating, dealing, people behind closed doors trying to decide who the nominee ought to be."

The problem for Dole was much more immediate than the convention, which is months away. The Kansas Republican was trying to keep his campaign alive in the face of a string of Bush victories.

"It's not over for Bob Dole," he told the Executives' Club of Chicago. And later at a news conference, Dole reiterated his determination to continue beyond today, "I've made a judgment that after Illinois, whatever happens, we're going to keep going."

But the outlook for the Kansas senator in today's primary was not good.

A Chicago Tribune poll said Bush was the choice of 62 percent of the likely GOP voters in Illinois, with only 28 percent for Dole.

Such a strong showing could give Bush a big chunk of the 82 Republican delegates at stake in Illinois. Added to his current total of 705 delegates, it could give him more than 60 percent of the 1139 needed to win the nomination at the GOP national convention in August. Dole has 165.

Despite the numbers, Bush told a reporter that suggestions he has locked up the nomination are premature.

"I feel the speculation has gotten ahead of the story," Bush said as he flew on Air Force Two from Chicago to Springfield, Ill. However, when asked if he were surprised that Dole was staying in the race, he replied, "I'm not sure I understand what he's doing."

On the Democratic side, Simon faced the fact that he has to win the Illinois primary to keep even his stripped-down campaign alive until the Democratic National Convention in July.

"I have no plans beyond tomorrow," he said in Chicago. "I have to win, and I will win. But obviously Michigan and Wisconsin come next."

A Chicago Tribune poll published yesterday suggested that Simon faces the possibility of a second-place finish.

The survey, conducted Friday and Saturday, said 32 percent of likely Democratic voters supported Jackson, 29 percent backed Simon and 20 percent said they would vote for Dukakis. Rep. Richard Gephardt (D.-Mo.) was the choice of 5 percent and Sen. Albert Gore Jr. (D.-Tenn.) had 4 percent.

The poll, conducted by Peter Hart Research Associates, interviewed 500 people and had a 5 percent potential margin of error.

An ABC News-Washington Post poll, conducted Saturday and Sunday and published in yesterday's Post, gave Simon the lead with 39 percent support to Jackson's 34 percent among very likely Democratic voters. Dukakis had 17 percent with Gore and Gephardt far behind. The potential sampling error was plus or minus 6 percentage points.

Going into the Illinois primary, Dukakis held the lead in the Associated Press delegate count, with 463 to 424 for Jackson. Gore had 353 and Simon just 36.