TRENTON -- The first phase of this year's New Jersey governor's race is over, and Phil Murphy, the early Democratic favorite, has emerged with a clean sweep of critical county endorsements.

By winning the backing of the Democratic committee in Cape May County on Sunday, Murphy, a millionaire former Goldman Sachs banking executive and ex-U.S. ambassador to Germany, has now earned the endorsement of the local party in all 21 counties in the state.

Such endorsements -- known as "county lines" -- are key in New Jersey. The winner gets their name placed at the top of the ballot in that county in the June 6 primary elections for the Democratic and Republican nominations to succeed Gov. Chris Christie, a term-limited Republican who is scheduled to leave office in January.

On the Republican side, the county endorsements were split between two candidates: Lt. Gov. Kim Guadagno and state Assemblyman Jack Ciattarelli.

Guadagno won the backing of the GOP in 14 counties, winning top-of-the-ballot placement in Atlantic, Bergen, Camden, Cape May, Cumberland, Gloucester, Hudson, Monmouth, Ocean, and Passaic. She also took Morris, Salem, Sussex, and Warren, but those counties do not award the top ballot spot.

Ciattarelli (R-Somerset) took Burlington, Essex, Hunterdon, Mercer, Middlesex, Somerset, and Union.

Monday kick-starts the next phase in the race. It's the deadline for candidates to hand in petitions with at least 1,000 signatures to run in both the Democratic and Republican primaries.

Murphy if facing a number of challengers in the Democratic primary, including former U.S. Treasury official Jim Johnson, state Sen. Raymond Lesniak (D-Union), and state Assemblyman John Wisniewski (D-Middlesex), among others.

A Fairleigh Dickinson University PublicMind poll released last month showed Murphy leading the Democratic field with 23 percent of the vote -- though 53 percent of Democratic-leaning New Jersey voters still say they don't know whom they'll support in the primary.

Johnson and Wisniewski received 4 percent, while Lesniak got 3 percent, and citizen activist Bill Brennan and community newspaper publisher Lisa McCormick both drew 2 percent.

Murphy has been bolstered by his fortune, having lent his campaign at least $10 million of his own money. He has also donated at least $1.15 million to Democratic candidates and organizations, including county parties, since 2001, according to an NJ Advance Media analysis.

His opponents have accused him of buying his support, but Murphy's campaign argues that the money he has given over the years has helped the Democratic Party grow in New Jersey.

"I am incredibly grateful for, and humbled by, the overwhelming support this campaign has received from the locally elected grassroots Democratic committee members here in Cape May and across New Jersey," Murphy said Sunday. "Since November, every crowd has been successively larger and more engaged, a real sign that Democrats are ready for a new direction for New Jersey."

The FDU poll showed Guadagno leading the Republican field at 24 percent, while Ciattarelli got 4 percent. Bergen County lawyer Dana Wefer drew 2 percent, while Nutley township commissioner Steven Rogers and Ocean County businessman Joseph Rullo both received 1 percent.

Brent Johnson may be reached at bjohnson@njadvancemedia.com. Follow him on Twitter @johnsb01. Find NJ.com Politics on Facebook.