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Patrick Semansky, Associated Press
Republican presidential candidate Ben Carson speaks at the National Sheriffs’ Association presidential forum, Tuesday, June 30, 2015, in Baltimore.

WASHINGTON — Conservative favorite Ben Carson's presidential campaign says it has raised more than $8.3 million in the last three months.

Campaign spokesman Doug Watts says the retired neurosurgeon received donations from more than 151,000 separate donors since launching an exploratory committee in early March. The fundraising totals are for money raised from then up through Tuesday.

Carson was the first Republican to release his quarterly fundraising totals, and the figures are a key test of viability for the first-time candidate. He is one of more than a dozen Republicans seeking the White House.

Watts says that no other campaign will "come even close to the number of engaged donors."

On the Democratic side, Hillary Rodham Clinton's campaign says it will report raising $45 million over the same time period.