Obama, Biden endorse Murphy in Florida Dem Senate primary
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President Obama and Vice President Biden are throwing their considerable weight into Florida’s contentious Democratic Senate primary, endorsing Rep. Patrick Murphy (D-Fla.), his campaign announced Wednesday.

Obama and Biden’s involvement amounts to a full-court press by the Democratic Party establishment on behalf of Murphy, who is running against liberal firebrand Rep. Alan GraysonAlan Mark GraysonPolitiFact cancels Alan Grayson hire after backlash Eighth Franken accuser comes forward as Dems call for resignation Pennsylania Dems file ethics complaint against Rep. Barletta MORE (D-Fla.)

The president called Murphy “a tireless champion for middle-class families” in a statement from the lawmaker’s campaign.

“I am proud to endorse Congressman Patrick Murphy for the United States Senate,” Obama said. “Floridians can count on Patrick Murphy to stand up for them every day as their next senator.”

Biden is set to campaign with Murphy in the Sunshine State on March 28.

While Obama has not made a public endorsement in the Democratic presidential race, the Florida primary serves as a proxy battle for that race. Murphy supports former Secretary of State Hillary ClintonHillary Diane Rodham ClintonKoch-backed group launches six-figure ad buy against Heitkamp Trump keeps up 'low IQ' attack on Maxine Waters GOP leaders to Trump: Leave Mueller alone MORE, while Grayson backs Sen. Bernie SandersBernard (Bernie) SandersAnti-abortion Dem wins primary fight Lipinski holds slim lead in tough Illinois primary fight Overnight Defense: Senate sides with Trump on military role in Yemen | Dem vets push for new war authorization on Iraq anniversary | General says time isn't 'right' for space corps MORE (I-Vt.)

The presidential endorsement is intended to be a shot in the arm for Murphy, who is running behind Grayson for a swing Senate seat being vacated by Republican presidential candidate Marco RubioMarco Antonio RubioRubio: McCabe 'should've been allowed to finish through the weekend' For Tillerson, bucking Trump became a job-killer At least six dead after pedestrian bridge collapses on cars in Florida MORE.

It comes one day after a Public Policy Polling survey showed Grayson leading Murphy 32 percent to 22 percent, though 45 percent of likely Democratic primary voters say they are undecided.

Republicans called the timing of Obama and Biden's involvement, one day after the poll's release, a sign that Democrats are concerned about the strength of Murphy's campaign. 

“Murphy's Washington handlers are hitting the panic button," said Greg Blair, a spokesman for the National Republican Senatorial Committee. "This is a candidate who has no credibility with his own party's base and the Democrat establishment is doing everything in its power to prop him up.”

Many top Democrats are hoping to end the bruising primary race to preserve their chances of winning in the general election.

Grayson has faced pressure to drop out of the race amid months of scrutiny over his business activities.

Senate Minority Leader Harry ReidHarry Mason ReidTrump presses GOP to change Senate rules Only thing Defense’s UFO probe proves is power of political favors Nevada Democrat accused of sexual harassment reconsiders retirement: report MORE (D-Nev.) last week called on Grayson to quit the campaign. He cast doubt on Grayson’s progressive bonafides and questioned the Florida congressman’s “moral compass" based on his handling of his hedge fund.

“These deeply troubling allegations should disqualify anyone from a seat in the U.S. Senate,” Reid said in a statement.

The Nevada senator accused Grayson of using his Senate office to unethically promote his Cayman Island hedge fund. The call came one day after The New York Times revealed top Grayson aides have urged him to shutter the fund, which he opened in 2011.

Grayson on Friday denied Reid's claims about the hedge fund and refused to drop out of the race.

"Sen. Reid may well prefer corrupt establishment errand boy Patrick Murphy, who routinely sells his vote to Wall Street lobbyists, and just last week hid from voting on his own bill providing amnesty to white-collar criminals," he said in a statement.

This report was updated at 11:44 a.m.