NEW YORK (Reuters) - As she looks ahead to the November White House election, Democratic candidate Hillary Clinton has hired the leader of a group that seeks to built political power among Latinos to help mobilize key voting communities.

U.S. Democratic presidential candidate Hillary Clinton speaks during a campaign stop in Sylmar, California, United States June 4, 2016. REUTERS/Mike Blake

Cristobal Alex, president of the non-partisan Latino Victory Project, will be the Clinton campaign’s new deputy director of voter outreach and mobilization, starting later this month, an aide said. Alex will work under Addisu Demissie, the national voter outreach and mobilization director.

Minority voters have been major blocs for Clinton as she has built a commanding lead over Senator Bernie Sanders, her rival for the Democratic nomination, and they could prove a crucial factor in the general election.

Among those minority voters are Latinos, a fast-growing group that, many activists say, has recently seen a spike in voter registration. Many activists point to presumptive Republican nominee Donald Trump as the spur for those registrations.

Seeking to portray himself as tough on illegal immigration, Trump has angered Latinos by saying Mexico is sending rapists and drug dealers over the border, and pledging to build a border wall that he says he will make Mexico pay for. Most recently, he has drawn criticism, including from senior Republicans, for saying a Mexican-American federal judge overseeing lawsuits involving fraud allegations against Trump University cannot do his job properly because of his Mexican heritage.

In contrast, both Clinton and Sanders have actively wooed Latino voters, releasing ads in Spanish and promising to hire Latinos to key cabinet positions.

But one complication when courting these voters is the difficulty in polling multi-lingual, multi-cultural communities.

“Throughout the election cycle we know that we are going to see a lot of really bad Latino polling,” said Matt Barreto, co-founder of research firm Latino Decisions and pollster for the Clinton campaign for Latino issues.

Barreto said that he has used “large sample surveys of Latino voters” for the campaign. “We are very confident that the Clinton campaign is taking all the necessary steps to gather the most accurate data possible on Latinos voters,” he added.

Clinton added to her delegate lead Sunday, when she won Puerto Rico’s primary. Primaries on Tuesday, when Clinton hopes to wrap up the nomination, include delegate-rich California, with a diverse population including Latinos, African Americans and Asian Americans.

Latino activists have warned Democrats that merely attacking Trump is not enough to win their votes, pressing for engagement on a range of issues.