There is little doubt who Democrats in the U.S. Senate are pulling for in Florida's smoldering Democratic primary to replace U.S. Sen. Marco Rubio.The day after outspoken Orlando congressman Alan Grayson officially entered the race on July 29 against U.S. Rep. Patrick Murphy, it touched off a financial stampede with Democrats in the Senate. Starting July 30, 15 senators used political action committees they control to pour $62,000 into Murphy's campaign over nine weeks, campaign finance records show. Seven of those members were making their first Senate campaign donations to Murphy, including Pennsylvania's Bob Casey, Ohio's Sherrod Brown and Missouri's Claire McCaskill, who is the keynote speaker at the Florida Democratic Party's annual meeting today in Orlando, where both Grayson and Murphy are also speaking.Murphy was already winning support from Democrats in the Senate in the spring when he filed. PACs controlled by Senate Minority Leader Harry Reid, Democratic Senatorial Campaign Committee chairman John Tester and Sen. Chuck Schumer, D-N.Y., were among eight to give Murphy a combined $35,000 through May.But as Grayson, a three-term congressman, ramped up his campaign and became more serious, Murphy's support exploded. Murphy now has almost $170,000 from 29 of the 46 Democrats in the Senate. That's nearly a two-thirds majority among Democratic senators, including Sen. Bill Nelson, a Florida Democrat, who gave Murphy $5,000 in June.Donations to Grayson's campaign from senators: 0."I've never seen anything like that," said Larry Sabato, a University of Virginia political science professor and analyst who has studied Congress for decades.Sabato said incumbents are typically hesitant to get involved in primary battles in other states unless it is to protect an incumbent they've served with or if a race is one-sided. Neither is the case in Florida, where Grayson and Murphy are locked in what many expect to be a competitive race.It has to be partly because of Grayson's reputation, Sabato said. The self-proclaimed "congressman with guts" has made a career out of often saying outrageous things that have brought him lots of national attention while making others — often in his own party — cringe. He came to prominence in 2009 when he used a floor speech in Congress to describe the Republican health care plan. "If you get sick in America, the Republican health care plan is this: Die quickly." He's since labeled Republicans "knuckle-dragging Neanderthals," suggested former Vice President Dick Cheney was a vampire, and declared a Federal Reserve Board adviser was a "K-Street whore." Many Democrats are convinced Grayson cannot carry Florida in a general election due to his reputation, which could leave them short of regaining the Senate majority."And if he does become Florida's senator, they have to be worried that he will make news that won't be beneficial for them," Sabato said.Donations from current senators could be good for both campaigns. For Murphy, in his second term in Congress, the funding shows how deep support is for the little-known 32-year-old congressman. Murphy's campaign spokesman, Joshua Karp, said Murphy is demonstrating he has support across Florida and the nation.For Grayson, who has less than $250,000 in his campaign account, it helps make the case that he is running against the Democratic establishment. Murphy has big-name supporters from other states in his corner, but Grayson will have the support of the grass roots progressive activists, said Grayson spokesman Kevin Franck.Grayson's reputation aside, Democrats giving to Murphy are more likely motivated by one key thing, said Nathan Gonzales, editor of the Rothenberg & Gonzalez political report."More concerning for Democrats would be serving with another freshman Republican than a Sen. Grayson," Gonzales said. Democrats are positioned to pick up the four seats they need to return to majority control — with the right candidates. Races in Florida, Wisconsin and Illinois are key targets. If they don't win the Florida seat, Democrats would have to knock off at least two of three Republicans in decidedly tougher races in Pennsylvania, Ohio and New Hampshire.The bottom line is that control of the Senate is "absolutely in play," Gonzales said. He said Senate Democrats already have concluded that to win in Florida they need to get behind a more moderate Democrat who can win Florida.Contact Jeremy Wallace at [email protected] or (850) 224-7263. Follow @jeremyswallace.