Undated (AP) _ Bob Dole declared Monday ''it's not over'' for his Republican presidential campaign despite indications of a big Illinois victory for George Bush, but Democrat Paul Simon 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, 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 1,800 in Carbondale, Ill. ''I tell you, we the people will win.''

Massachusetts Gov. Michael Dukakis, lying third, sought a good enough showing to keep up some momentum from Super Tuesday. Over and over on Monday, Dukakis hammered at Simon's contention that the Democratic convention will be deadlocked.

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

Dukakis apparently wasn't the only Democrat wanting to avoid a brokered convention. Democratic Chairman Paul Kirk suggested Monday he would try to rally uncommitted delegates behind whichever candidate is leading the field at the end of the primary season, if none has a lock on the nomination.

Kirk said in a telephone interview from New York that he didn't want to ''leave the impression that Kirk's going to be the broker'' but said he would be ''in the middle'' of efforts to avoid hurting the nominee with a battle just before or during the convention.

The problem for Dole was much more immediate than the conventions, months away in the summer. The Kansas Republican was looking for a way 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.

Later, at a news conference, Dole repeated his determination to continue beyond Tuesday: ''I've made a judgment that Illinois, whatever happens, we're going to keep going.''

The Kansas senator said he had ''made some inroads'' against Bush in Illinois, but that there had not been enough time to stop Bush's surge after a 16-state win last Tuesday.

''You want to elect momentum or elect the better candidate?'' he asked the Executives Club audience. ''Maybe it's going to take a couple of weeks for everything to sort of slow down.''

But the Illinois outlook for Dole 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 1,139 needed to win the nomination at the GOP National Convention in New Orleans 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 was facing the reality 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.''

And second place isn't good enough.

''A strong second isn't very strong,'' Simon told a reporter. If he does end up in second place in either delegates or the popular vote in Illinois, he said, ''I'd have to reevaluate.''

One poll published Monday in the Chicago Tribune suggested 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 of Missouri was the choice of 5 percent and Sen. Albert Gore Jr. of Tennessee had the backing of 4 percent.

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

An ABC News-Washington Post tracking poll published in Tuesday's editions of the 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 in the survey, conducted Saturday and Sunday, 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.

A total of 173 delegates are at stake on the Democratic side in Illinois.

One Dukakis goal is to win some of those delegates, a difficult task given the complicated nature of the state's ballot. Voters not only cast ballots for presidential candidates, they also vote directly for delegate candidates. Thus, a vote for Dukakis in the ''beauty contest'' portion does not necessarily mean a vote for him in the delegate selection process.

Another goal, Dukakis aides said privately, is to narrow the Democratic field. Mentioning the polls showing Dukakis drawing his last-minute support from Simon's voters, the governor's aides said they would be delighted to see Jackson beat Simon, believing it would drive the senator from the race.

Republican Pat Robertson was to be in Washington on primary day, where he planned to meet with the visiting Israeli prime minister, Yitzhak Shamir. The Robertson campaign characterized it as a meeting of ''two old friends.''