...how did all these bizarre strong third party/independent candidacies for senate and governor occur? And can someone give the background for each individual race with these candidates?
Let's see:
Florida: Crist is encouraged to enter the Republican primary by the NRSC to keep the seat safe, and Dems basically put up a sacrificial nominee. However, Marco Rubio surges in the primary and general, and around April Crist decides that he's got no shot whatsoever at beating him, so he enters as an independent, hoping to get enough Democratic voters to put him over Rubio in the general. However, Meek has done a decent job at keeping the Democratic base, which has left Rubio up a bunch against two candidates battling for the Center-left.
Alaska: Incumbent Republican Lisa Murkowsi lost a close primary to Joe Miller, and after flirting with assuming the Libertarian party line, decided to just conduct a write-in campaign instead. Like Florida, this basically kills the Democrat's chances at winning, as the Independent takes more of the Democratic vote than the Republican vote.
Massachusetts: Deval Patrick is running for re-election against Charlie Baker, and former Democrat Cahill has entered the race as an independent, though seems to have faded recently. Don't really know much more on this one.
Colorado: Republican Dan Maes has serious ethics problems (though so did his primary opponent) and is getting killed in 1-on-1 polls with Denver Mayor Hickenlooper. Tom Tancredo, a former Republican congressman from South Denver suburbs, threatened to enter the race if Maes didn't step aside and let the GOP nominate someone better, but Maes refused and Tancredo has followed up on his promise.
Delaware (maybe): Incumbent Congressman Mike Castle ran for Senator, but was beaten by Christine O'Donnell, turning a likely GOP pickup into a likely Democrat hold. Castle has been talking about running a write-in campaign, which might take enough votes from Chris Coons to give O'Donnell the edge.
Minnesota Governor: Don't know much about this one to be honest. SOmeone else can tell you more
Maine Governor: Same as above, although Tea-Party favorite LePaule looks like he would be winning even without a split Left.
That's all I can think of aside from a few Democratic plants in the form of "Tea Party" candidates, who are there to suck off Republican votes.