SAN JUAN, Puerto Rico (CNN) -- Sen. Hillary Clinton is spending her second straight weekend campaigning in Puerto Rico before the island territory's June 1 primary. It could be one of her last chances to boost her popular vote total.
For Clinton, it's a family affair -- with both husband Bill and daughter Chelsea making the rounds.
"Chelsea and I and Hillary have now been to 42 of Puerto Rico's municipalities campaigning for the votes of the people of Puerto Rico," Bill Clinton said Thursday.
"She represents more Puerto Ricans than anyone in the world except someone who is elected here. Send the message back to the mainland on Sunday that Puerto Rico deserves to be considered and its potential is unlimited if only you had a genuine partner in the White House," he added.
She's counting on a strong showing on Sunday. With 55 delegates up for grabs Tuesday, it's the last big prize before the primaries end. Watch as Clinton looks ahead to Puerto Rico »
According to the new survey conducted for the newspaper El Vocero and Univision, Clinton is leading Obama there 51 percent to 38 percent among all adults in the primary.
The poll also show 52 percent of Puerto Ricans view Clinton favorably while 42 percent view Obama favorably. Watch Clinton campaign in Puerto Rico »
The survey was conducted May 8-20. Given the length of the survey time, it is possible it may not reflect the current views of Puerto Ricans since both candidates have visited the island since the polling began, and other recent developments on the campaign trail may have swayed voters' minds there.
Her popularity on the island caught the attention of one of the island's most famous pop stars Thursday.
Ricky Martin endorsed Clinton for the Democratic nomination, saying, "Whether fighting for better education, universal health care and social well-being, as first lady and senator from New York -- representing millions of Latinos -- she has always fought for what is most important for our families."
Obama, meanwhile, briefly campaigned in Puerto Rico last weekend.
On Saturday, he marched along a street in Bayamon, shaking hands with supporters as he walked in front of a banner that said "Puerto Rico Con Obama."
This event was referred to as a "caminata," a traditional parade for a candidate. Watch Obama dance up the parade route »
Obama remarked to the crowd, "I will never forget the support and the friendship that I've seen here in Puerto Rico. ... I am absolutely confident that if that we keep on working hard, there's no reason why we can't win here in Puerto Rico, and if we win Puerto Rico, we will win the nomination."
The Illinois senator is ahead in the pledged delegate count, according to CNN's latest count. Clinton has 1,499 pledged delegates to Obama's 1,661.
While Puerto Rico gets to vote in the primaries, it is not allowed to vote in the general election. The Democratic and Republican parties run the primaries and caucuses, and they allow U.S. territories, like Puerto Rico, to take part in the process.
But only the 50 states and the District of Columbia vote in the general election, as mandated by the Constitution.
CNN's Ed Hornick, Alexander Mooney and Lauren Kornreich contributed to this report.