Edward Kennedy, the venerable Democratic Party stalwart who underwent surgery for a brain tumour this summer, could be planning a surprise appearance as the Democratic nominating convention opens on Monday. Kennedy secretly flew to the convention site in Denver, Colorado on Sunday night, after aides had earlier said the Massachusetts senator was unlikely to make the trip because of his health, the Washington Post reported. Kennedy, 76 and only surviving brother of slain president John F Kennedy, was an early and vocal supporter of presumptive Democratic nominee Barack Obama. The third-longest serving senator in US history, Kennedy was diagnosed with a malignant brain tumour in mid- May and has since been recuperating from a successful surgery, the dpa reported. But it remained uncertain whether he would actually speak at the convention Monday on a night highlighted by Obama's wife Michelle. The official schedule had included a video-taped message from Kennedy. The scramble for the White House was dead even between Obama and presumptive Republican nominee John McCain, according to two separate polls released late Sunday, the eve of the convention's opening. A Gallup Poll showed each candidate with 45 per cent support from registered voters, while a CNN/Opinion Research Corp poll showed a 47-per-cent stalemate. The polls delivered sobering prospects to Senator Obama, 47, as his party's delegates head to Denver to formally nominate him and launch the final push to reclaim the White House from the Republicans. They were the first national polls taken after Obama named Senator Joe Biden, a top voice on foreign policy in the Democratic Party, as his presumptive vice presidential candidate on Saturday. Normally, presidential hopefuls get a boost in the polls when they name their running mate. Obama had edged ahead of McCain most of the summer, but his lead has narrowed since early August - to just 1.6 per cent late last week, according to an average compiled by realclearpolitics.com. Pollsters raised the possibility that Obama has lost ground with women voters disappointed by his vice presidential announcement. In June, 75 per cent of the backers of his chief rival in the primary campaign - Hillary Clinton - said they would back Obama, according to CNN figures. That number has fallen to 66 per cent, CNN reported. Gallup figures however showed that Obama still has 49 per cent of women polled in his corner, versus 39 per cent for McCain. McCain has more support from men - 48 per cent - than Obama, with 42 per cent. During the four-day convention in Denver, in the foothills of the Rocky Mountains, the party's 4,400 delegates will cast their votes for Obama and Clinton - who won more than 40 per cent of the primary vote - on Wednesday night. Clinton, who has been campaigning for Obama this summer, is expected to release her delegates to support Obama. Hundreds of demonstrators marched through downtown Denver on Sunday, under the watchful presence of dozens of mounted police officers and ground forces in full riot gear. They were protesting the war in Iraq and the inequities of the US two-party system. Denver police officials reported few disturbances and said only four arrests had been made on the day. Obama is campaigning through the Midwest while his party meets in Denver, and won't appear until Thursday to make his acceptance speech before 75,000 people at Invesco Field. On Monday, Michelle Obama and other family members are expected to present the personal side of Obama, still a relative unknown for many Americans. McCain will head to St Paul, Minnesota, for the September 1 opening of the Republican Party nominating convention. General elections are November 4.