With John McCain closer than ever to being the Republican candidate for president, Democratic leaders are sounding the alarms about a worst-case scenario in which their party has no apparent nominee until the national convention in late August, leaving them with just over two months to mount a general election campaign.

Florida Sen. Bill Nelson, speaking on the floor of the Senate, warned Friday that it would be a “train wreck” for the party if Barack Obama and Hillary Clinton cannot break their deadlock soon.

“Here is the coming train wreck,” Nelson said. “If one of our two leading candidates does not get a majority by the time that all the primaries and caucuses are over … then we go into a period during June, July and all the way to the end of August at the National Democratic Convention, a period of enormous uncertainty and turmoil.”

He said part of the turmoil would be the backroom deal-making of “superdelegates” — elected officials and other party leaders who come to the convention uncommitted to any candidate — and the fact that Florida’s and Michigan’s delegates will not be seated at the convention. Those two states were stripped of their delegates for holding primaries before Super Tuesday, in violation of party rules.

Clinton won the primaries in both states, and seating their delegations would benefit her.

Democratic National Committee Chairman Howard Dean has also said he fears an intra-party showdown at the convention in Denver.

Dean has suggested that Florida and Michigan hold caucuses to select delegates, but Nelson, who has endorsed Clinton, said “you can’t undo an election with caucuses.”

Dean, who calls McCain a “media darling,” has warned about the same worst-case scenario.

He recently told a New York TV station, “The idea that we can afford to have a big fight at the convention and then win the race in the next eight weeks, I think, is not a good scenario … I think we will have a nominee sometime in the middle of March or April. But if we don’t, then we’re going to have to get the candidates together and make some kind of an arrangement.”

He didn’t say what that arrangement would be.

Three days after Super Tuesday, delegate tallies by The Associated Press show Clinton with 1,045 delegates and Obama with 960. A candidate needs 2,025 delegates to clinch the nominationl; both candidates are about halfway there.

McCain needs only a few hundred more delegates to guarantee victory; Mitt Romney’s exit from the race on Thursday left McCain as the odds-on nominee, although Mike Huckabee and Ron Paul are still officially running for the GOP nomination.

Republicans who have clashed with McCain in the past have begun to accept his candidacy, even though some conservatives — like Focus on the Family founder James Dobson, who endorsed Mike Huckabee Thursday night — say McCain and his moderate positions will never be palatable to the right.

And McCain has already started his general election campaign, focusing on Obama’s and Clinton’s positions on Iraq and taking them on in tandem as a singular threat to conservatives.

He continued his assault on the candidates Friday, after speaking at a national security round-table in Norfolk ahead of Virginia’s primary Feb. 12.

“All I can say is that they want to set a date for withdrawal,” McCain said. “There would be catastrophic consequences … There is a fundamental misunderstanding on the part of both of them as to what’s at stake and a failure to recognize that our strategy under General Petraeus, called the surge, has been succeeding. That, I think, will be a major issue in this campaign.”

Obama and Clinton have tried to return fire — Clinton complained yesterday about his economic and military policies — but their quest for delegates keeps them focused on each other.

This leaves McCain in the enviable role of statesman, senator and party figurehead, observers say, unshackled from the once-consuming battle among a dizzying field of Republican candidates.

Democratic pollster Doug Schoen told FOX News, “With John McCain the Republican nominee, if he can get the right in line with his candidacy, and the Democrats remain divided, it’ll make a Democratic victory more unlikely in November.”

McCain’s National Finance Co-Chairman Fred Malek said McCain will now be able to show leadership on Capitol Hill, and not just the campaign trail.

“While Hillary Clinton and Barack Obama are out on the campaign trail kind of fighting each other on things, John McCain can be back in the Senate leading the charge on issues that are really important to the American people.”

Despite tasting victory, McCain said he will not discount Huckabee, who said Friday that it’s not a lock for the Arizona senator.

“An election is about a choice, not a coronation,” Huckabee said in Kansas.

McCain fended off discussion of potential running mates, as rumors continue to swirl that Huckabee could be a contender.

“Governor Huckabee is still in this race and he is a viable candidate and I am sure will continue to show strength,” McCain said in Norfolk.

FOX News’ Mike Majchrowitz and Mosheh Oinounou contributed to this report.