Former New York City Mayor Michael Bloomberg will host a fundraiser for Sen. Brian Schatz (D-Hawaii), a major money boost for the freshman lawmaker who is facing a tough primary.

Bloomberg, who just left the top job in New York City, will headline Thursday's event in Hawaii. 

The event will help Schatz bolster his fundraising edge but could hurt his efforts to paint himself as the more liberal candidate in the race given Bloomberg's status as Republican turned Independent.

Schatz's primary opponent, Rep. Colleen Hanabusa (D-Hawaii), is attacking him for the $1,000 per person fundraiser, blasting Bloomberg's record as mayor.

"Bloomberg spent a lot of his time in New York making bad decisions for working families, and balancing the budget by pushing cuts to programs for children, education, benefits and pensions," her campaign says in a fundraising email. "He was on the wrong side of every issue that affect people who work and sacrifice for every dollar while worrying about their future. The very issues that we know are so important to so many families in Hawaii."

Schatz has the backing of the Progressive Campaign Change Committee, a group that backs more liberal candidates in primaries, as well as from liberal favorites like Sens. Elizabeth Warren (D-Mass.) and Sherrod Brown (D-Ohio). He's made Social Security expansion a cornerstone of his campaign.

Schatz's campaign touted Bloomberg's work for gun control and climate change legislation.

"Senator Schatz is pleased to have the support of the mayor given his leadership on common sense gun safety legislation and strong promotion of clean energy production to slow the effects of climate change," Schatz campaign manager Clay Schroers says in a statement. "Senator Schatz's priority is always delivering for Hawaii, and effective leadership in the Senate for Hawaii means developing relationships with leaders across the country."

The primary is dividing Democrats in the state. The late Sen. Daniel Inouye's (D-Hawaii) deathbed wish was for Hanabusa to be appointed to replace him. But Gov. Neil Abercrombie (D) gave Schatz the job instead and she decided to challenge him for the seat.

Polls show a tight race. The primary is August 9.

This post was updated at 1:55 p.m.