Monday's observance of what would have been Martin Luther King Jr.'s 90th birthday is emerging as an important moment for Democrats eyeing the White House to talk about one of the most divisive issues in politics: race.

At least a half dozen declared or potential presidential candidates will attend events and talk about what King's legacy means to Americans in 2019.

It's a sign of the wide-open nature of the 2020 field, which is likely to include several candidates of color for the first time.

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