As New York City voters head to the polls to cast their ballots in the largest Super Tuesday ever, many city residents are also heading to Lower Manhattan for a tickertape parade celebrating the Giants’s Super Bowl win.

The addition of the parade to today’s calendar is raising concerns among some political observers who say the football celebration may dissuade some voters from going to the polls and could cause problems for the city’s Board of Elections, which has its headquarters along the parade route.

To prepare for the crush of spectators expected to line Broadway to cheer on the championship team, the Board of Elections is working with the police department to ensure voters traveling to polling sites along the parade route will be able to get in, cast their votes, and leave without a problem.

Mayor Bloomberg said yesterday that he didn’t think the parade would impede the primary, and he defended holding it on Super Tuesday, when more than 20 states hold presidential primaries.

“Voting doesn’t take more than a couple of minutes,” he said yesterday. “A lot of people have the day off, so they can vote and can work at the polls, and that is what democracy is all about,” he added.

A professor of public affairs at Baruch College, Douglas Muzzio said he didn’t understand why the parade couldn’t be held later this week or even next week.

“Why would you take away from an extremely important set of primaries? You risk impeding the election process,” he said. “I don’t know how many people might otherwise have voted but went to the parade, but no matter how few a number, in close races it could make a difference.”

Mr. Bloomberg argued that it made the most sense to hold the parade today because the team only returned to New York yesterday and by tomorrow would “start going to the four corners of the earth and have other things to do.”

The parade appears to be no deterrent for supporters of the Democratic and Republican candidates, who have taken to the city’s streets in recent days to distribute signs and stickers, staff phone banks, and rally voters to support their favorite candidate today.

Polls show Senator Clinton beating Senator Obama in New York, with a Quinnipiac University poll released yesterday saying she would capture 53% of the vote among likely Democratic primary voters, compared to Mr. Obama’s 39%. Senator McCain was ahead of the Republican pack in New York, securing a 54% lead in the poll. Mitt Romney trailed with 22 points.

Even though he lags behind in the polls, Mr. Obama still can win New York delegates today. The director of the Quinnipiac University Polling Institute, Maurice Carroll, said the senator would likely pick them up in districts with a high concentration of black voters and young voters.

The Democratic candidates are competing for 232 delegate votes in New York. There are 370 delegate votes at stake for the Democratic candidates in California.

Today’s primary will allow Mrs. Clinton to put her home-state volunteer army to work; more than 25,000 volunteers have signed up online to help her in New York today, her campaign said.

The campaign is holding parties on college campuses and in homes, with supporters of Mrs. Clinton bringing their own cell phones to call voters. It also has hundreds of phone lines available for phone banking, a spokesman for the Clinton campaign, Blake Zeff, wrote in an e-mail message.

Mr. Obama’s campaign has more than 10,000 volunteers in New York State, with more than 7,000 in the city.

“We will be at subway stops, polling places, and other places around the state getting out information,” a spokesman for the Obama campaign, Richard Fife, said, adding that the campaign wants to make sure that the last thing voters see before heading to the polls is “something for Barack Obama.”

The Republican front-runner, Mr. McCain, packed more than 500 people into a firehouse in Hamilton, N.J., near Trenton, where he was joined by a handful of top supporters, including Mayor Giuliani and Rep. Vito Fossella, a former Giuliani backer who represents Staten Island and part of Brooklyn.

Mr. Giuliani drew cheers from the crowd rivaling those given Mr. McCain, but his role yesterday was merely as surrogate. He called the Arizona senator a “50-state candidate” who could compete in Democratic stronghold states such as New York, New Jersey, and Connecticut that Republicans have all but abandoned in recent presidential elections.

Mr. McCain later appeared briefly at Grand Central Terminal to accept the endorsement of Governor Pataki, who hailed him as a Republican who could appeal not only to conservative but to “intelligent independents and moderate Democrats.”

In a preview of a possible general election battle, a cadre of Clinton supporters showed up to surround the McCain fans providing a backdrop for the television cameras.

Mr. McCain will bounce along each coast tomorrow to secure support in the crucial New York and California primaries. He is scheduled to attend a rally at Rockefeller Center Plaza early this morning with Mr. Giuliani and other elected officials and then catch a plane to San Diego for another get-out-the-vote event.

Mr. Romney is heading to West Virginia to address a convention of state delegates and then flying to Boston to vote in the Massachusetts primary and watch the results come in at the Boston Convention and Exhibition Center. Michael Huckabee will be in West Virginia at the same event and then travel to Little Rock, Ark.

Mr. Obama will fly to his home state of Illinois for a Super Tuesday celebration at the Hyatt Regency hotel in Chicago this evening. Mrs. Clinton will take in the results from Manhattan Center Studios.

A government reform coordinator at the New York Public Interest Research Group, Neal Rosenstein, said he is bracing for a record amount of calls on the group’s voter help line for a presidential primary.

“There’s a wide open race. There’s no incumbent running president, there’s hometown candidates on the ballot, there’s tremendous interest by young people and new voters as well,” he said. “So yeah, I’m expecting a lot of folks not only calling our help line but turning out to the polls.”

Plans for the ticker-tape parade prompted the Board of Elections to switch up its normal routine yesterday and move back-up ballot marking devices, which help voters mark paper ballots and are normally stored in the main office, to other boroughs, where there’s little danger that access to them would be limited by the spectators cheering on the Giants.

A spokeswoman for the Board of Elections, Valerie Vazquez, said she hopes the parade “won’t be a deterrent” to eligible voters. “Some of it really is out of our control because of the obvious congestion,” she said.

There are about 2.8 million registered Democrats and more than half a million registered Republicans in New York City, according to figures from the state Board of Elections released in November. Only registered Democrats and Republicans can vote in today’s primary.