On this day in 1986 the space shuttle Challenger explodes over Cape Canaveral, Fla. Also on this day, in 1973, the Paris Peace Accords are reached formally ending America's involvement in the Vietnam war. On to today's top stories:

"Kennedy Will Endorse Obama In Blow to Clinton" (Shailagh Murray and Anne Kornblut, Washington Post) Hillary Clinton had barely stepped off the plane from her bruising defeat in South Carolina before she heard the news that the Kennedy Clan -- with the exception of RFK's kids -- has thrown its support to Obama. Aside from boosting Obama in Massachusetts, the endorsement also gives the upstart candidate some needed establishment support nationwide.

"Florida Primary Turnout May Set Record" (Gary Fineout, Miami Herald) Nearly one million Florida voters have already cast ballots ahead of tomorrow's election. A few weeks ago the chattering class would have said this surely helps Rudy Giuliani, who's been in the state for almost the whole month. But that's no longer the case, as the race has come down to a match between John McCain and Mitt Romney.

"Romney Focuses on Economy" (Glen Johnson, Associated Press) With polls showing that the economy is the No. 1 issue with Florida voters, Mitt Romney has spoken about little else, even chastising opponent McCain for admitting economic matters are not his forte. Romney, however, did talk about the scenery: "Cuban-American woman are gorgeous," he said.

"Obama Gains But Still Lags in Big States" (Christopher Cooper and Amy Chozick, Wall Street Journal) He might be the new JFK, but Obama still has a long road ahead of him to reach the nomination. First stop: Super Tuesday, where Clinton leads in nearly every state except Georgia and Obama's home state of Illinois.

"Giuliani Falls Far Behind in Florida" (Joseph Curl and Sean Lengell, Washington Times) Of all the sub-plots of Election 08, few have been as fascinating as the rise and fall of Rudy. Along with his national lead, Giuliani has watched his lead in Florida shrink dramatically -- which is particularly irksome considering that Rudy hasn't done much else but campaign there all month.

"For Clinton, Obama, Florida Primary Is About Expectations" (Billy House and William March, Tampa Tribune) Who's that Democrat that will join the Republicans in Florida tomorrow night? Why, it's Hillary, who currently holds a monster lead in the Sunshine State. Which is great for her, except that Florida won't get any delegates. So Clinton's presence is a way to bring national attention to a -- theoretically -- inconsequential state.

"McCain, Long a G.O.P. Maverick, Is Gaining Mainstream Support" (John Broder, New York Times) What a trip it's been for McCain: From maverick, to frontrunner, to dead-in-the-water, to establishment candidate. Picking up some major establishment cred in Florida over the last few days, a victory there for McCain would likely propel him to legitimate frontrunner status again. A loss? Well, who knows ...?

"In GOP, Some Averse to McCain Politics, Manner" (Jill Zuckman, Chicago Tribune) If McCain does lose tomorrow, it will likely be because he couldn't convince conservative Republicans that he's one of them. At the same time, while picking up some establishment support, there are still many Washington Republicans who can't forget what they see as McCain's grandstanding on certain issues, often at the expense of party unity.

"Races Entering Complex Phase Over Delegates" (Adam Nagourney, New York Times) As Obama campaign manager David Plouffe says in this article, "At the end of the day, this is a delegate race." Maybe it will be. But that's the calculation all the candidates have to confront heading into Super Tuesday, where the race for big states and a lot of delegates begins.

Get today's other election stories at RCP's Politics and Election page.