Phil Rosen, a co-chair of Weil Gotshal’s real estate practice and well-known Jewish leader, has officially endorsed Marco Rubio and will serve as a foreign policy advisor for the campaign. Rosen, one of Mitt Romney’s top bundlers in 2012, was highly sought after by several candidates. Rosen told Jewish Insider, “For several months I’ve been talking with most of the 2016 Republican field about their individual campaigns, paths to victory and policy positions.” Rosen noted that although he’s impressed with the candidates and finds this cycle’s field to be “light years ahead of, and better than most of, the 2012 candidates,” he made the “difficult” decision to “throw my weight behind Senator Marco Rubio.”

When asked what specifically led to his endorsement, Rosen listed Rubio’s foreign policy experience and knowledge and said that is “something we desperately need at this troubling point in time for the U.S. and the world.” He called Rubio “the strongest supporter of the U.S.’s best friend on the world stage, Israel.” Lastly, Rosen said he thinks Rubio can attract the “necessary and desirable” support from youth voters, Hispanic voters and female voters.

Besides helping Rubio with fundraising, Rosen has agreed to serve as a senior foreign policy advisor for the campaign. Rosen said he was “thrilled” at the opportunity to serve with Rubio whom he called “dynamic, electrifying, intelligent and patriotic.”

Rosen’s endorsement is significant for a few reasons.

1. Fundraising. Rosen is one of the leading bundlers in presidential politics. According to two sources, it is believed that Rosen raised around $5 million for Mitt Romney in 2012.

2. Sheldon Adelson. Rosen is close with Sheldon Adelson, with whom he serves on the boards of the Republican Jewish Coalition (RJC) and Birthright Israel. Adelson is already rumored to be favoring Rubio and the favorable coverage of Rubio in his newspaper, Israel Hayom, has been quite noticeable. Adding a super-lawyer like Rosen can only help Rubio close the deal.

3. Walker v. Rubio Bellwether. Rosen, who is very well connected in New York City fundraising circles, is believed to have deliberated between Walker and Rubio for a while. In the past few months, Rosen attended donor gatherings for Walker hosted by the Ricketts family in Las Vegas and New York. As the Washington Post reported last week, Walker has struggled to make inroads among NYC donors and Rosen, perhaps, serves as a bellwether for others deciding between Walker and Rubio. It has yet to be determined whether Paul Singer, the top political donor of 2014 and who is also rumored to be deciding between Rubio and Walker, follows suit.

4. Ted Cruz’s electability: According to Ted Cruz’s April FEC filing, Phil Rosen donated $2,700 to Cruz for President. While donors like Rosen might admire Cruz, many are concerned about his electability and Rosen’s Rubio endorsement is a reminder of that.