Republican U.S. Sen. Marco Rubio has reversed his decision to retire from the Senate at the end of this Congress and will run for a second term. In doing so, he has breathed new life into the GOP's chances of holding the seat, but that doesn't mean that he has become anything more than the very slightest of favorites in November. The race will remain in the Toss Up column. Rubio's decision not to seek a second term allowed him to focus on his quest for the Republican presidential nomination. He ended his bid for the nomination on March 15 after coming in second, behind Trump, in the Florida primary. At the time, he assured anyone who asked that he wouldn't change his mind about running for re-election. In recent weeks, though, he has come under increased pressure from GOP leaders in Washington and in Florida to rethink his decision. The mass shooting in Orlando became another factor in Rubio's consideration, although Democrats are quick to accuse him of opportunism. Republicans have been dealing with an unwieldy, largely unknown and

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